Martin Gomez, the father of Kassandra B. and Nicholas B., children born out of wedlock, contests their adoption by appellants, Timothy L. Savage and Karen M. Savage. The birth mother, Anita Bechtold, had given custody of the two children to an adoption agency, K.E.S.I.L., for the purpose of adoption. Bechtold falsely told K.E.S.I.L. that she did not know the identity of the children’s father(s). K.E.S.I.L. placed the children in the Savages’ home, and the Savages eventually filed an adoption petition in the county court for Cass County. Gomez discovered the pending adoptions, entered his *914opposition, and sought custody of the children. After a hearing, the county court terminated Gomez’ and Bechtold’s parental rights and placed custody of the children in K.E.S.I.L. for placement with a suitable adoptive family. No adoption decree was either entered or denied. The district court for Cass County reversed the county court’s order terminating Gomez’ rights. The Court of Appeals affirmed the district court and granted Gomez immediate custody of the children because Bechtold had relinquished her parental rights. We granted further review. Our review of the record reveals that the county court was without statutory authority to exercise subject matter jurisdiction so as to entertain the adoption proceedings in which parental rights were terminated. A judgment entered by a court which lacks the authority to exercise subject matter jurisdiction is void. We therefore vacate the orders of the county court terminating parental rights and placing custody in K.E.S.I.L. and remand the cause to the Court of Appeals with directions to remand to the district court for further remand to the county court to dismiss.
BACKGROUND
Gomez and Bechtold met when they were teenagers. They began dating, and on July 23, 1982, they had a child, Jamie. Although they never married, Gomez and Bechtold began living together in 1984. The couple had two more children, Kassandra, bom May 4, 1986, and Nicholas, bom July 17, 1989. Gomez was not identified as the father on any of the children’s birth certificates, but the parties have stipulated that he is the biological father.
In or about 1986, Gomez left Bechtold and the then two children for about 6 months and moved to another state. During that time, he provided no support for his children and did not contact them or their mother. However, Gomez and Bechtold reunited in December 1987.
During the time that Gomez and Bechtold lived together, both worked at various jobs with some periods of unemployment. Gomez partially supported Bechtold and the children with his wages, unemployment income, and a workers’ compensation settlement. Bechtold attended cosmetology school *915for 14 months and began a career in hairstyling in 1989.
Gomez and Bechtold separated on August 10, 1990, after Bechtold asked Gomez to leave. Gomez maintained some contact with his children but provided little financial support. During 1990, Gomez gave Bechtold about $400 to $500 and earned approximately $7,500. Gomez talked with his children once or twice a week by phone and took them for occasional excursions and visits.
Gomez has a history of alcohol abuse and has been arrested several times for driving while under the influence and for disorderly conduct. He has admitted to smoking marijuana in the past.
Bechtold testified that during the summer of 1991, she was having a difficult time financially. Bechtold did not think she could take care of the children by herself, and she concluded that she could not rely on Gomez for any financial support. Bechtold decided to place the two younger children for adoption.
Bechtold contacted an adoption agency in California and learned that she needed Gomez’ consent before the children could be placed for adoption. Bechtold discussed adoption with Gomez, but he refused to give his consent.
In October 1991, Bechtold contacted the K.E.S.I.L. adoption agency. Knowing she needed Gomez’ consent, Bechtold lied to K.E.S.I.L. and stated that she did not know the identity of the children’s father(s). Bechtold placed Kassandra and Nicholas in K.E.S.I.L.’s custody on October 19. On November 2, Bechtold signed relinquishment forms for each child.
On the same day that Bechtold signed the relinquishment forms, Kassandra and Nicholas were placed with appellants, the Savages. The Savages signed a “Child Acceptance Agreement,” in which they acknowledged that K.E.S.I.L. had advised them that “until finalization in Nebraska Courts, this adoptive placement is one they term ‘legal risk’ [sic] because the birth fathers of the children have not been named, identified on the child’s birth records or signed a relinquishment of parental rights.” K.E.S.I.L. was paid $7,500 by the Savages.
Gomez learned on November 11, 1991, that the two children had been placed for adoption, when he telephoned Bechtold to *916discuss the children’s attendance at his upcoming wedding. Bechtold told Gomez that she had placed the children for adoption but refused to give him any further information. Gomez asked a friend of his mother, an attorney, for advice. At the attorney’s suggestion, Gomez filed two “Notice of Intent to Claim Paternity” forms with the Department of Social Services (DSS) on November 12, 1991. It was not until July 1992 that an employee of K.E.S.I.L. informed the Savages of the existence of Gomez and his paternity claims.
On October 20, 1992, the Savages filed a petition for adoption in the county court for Cass County. In their petition, the Savages stated that Bechtold had relinquished the children to the care, custody, and control of K.E.S.I.L. As required by Neb. Rev. Stat. § 43-102 (Reissue 1988), the Savages attached to the petition consents from K.E.S.I.L. and the mother. Their petition further alleged that a notice of intent to claim paternity was filed with DSS by Gomez claiming paternal rights to the children. Their petition further alleged that the claim of paternity should not be recognized by the court pursuant to the provisions of Neb. Rev. Stat. § 43-104.02 (Reissue 1993) for the reason that such claim is barred by not having been filed within 5 days after the birth of each of the children.
By order of the county court, Gomez received notice of the Savages’ adoption petition. Gomez filed a motion in opposition to the adoption and a request for custody citing Neb. Rev. Stat. § 43-104.06 (Reissue 1993). On July 20 and 21, 1993, the county court conducted a hearing regarding the adoption petitions and Gomez’ opposition.
By its order dated August 23, 1993, the county court held Bechtold’s parental rights had been terminated by reason of her relinquishments. The county court, referring to Neb. Rev. Stat. § 43-292(2), (3), and (4) (Reissue 1993), of the Nebraska Juvenile Code, concluded Gomez was not a fit parent and terminated Gomez’ parental rights. The county court placed custody of the children with K.E.S.I.L. for suitable placement with an adoptive family.
Gomez appealed to the district court for Cass County. The district court held that the county court was without jurisdiction to consider termination of Gomez’ parental rights under the *917juvenile code. The district court reversed the holdings of the county court and remanded the matter for further proceedings.
The Savages appealed to the Nebraska Court of Appeals. In re Adoption of Kassandra B. & Nicholas B., 3 Neb. App. 180, 524 N.W.2d 821 (1994). That court also concluded that the county court was without jurisdiction to terminate Gomez’ parental rights under the juvenile code. Further, the Court of Appeals held that no adoption could be decreed by the county court because none of the provisions found in Neb. Rev. Stat. § 43-104 (Reissue 1993) that obviate the need to obtain parental consent for adoption were met. However, the Court of Appeals held that the district court erred in its mandate to the county court. Rather than remanding for further proceedings, the Court of Appeals held that the law clearly entitled Gomez, who was not an unfit parent, to the immediate custody of his children. We granted the Savages’ petition for further review.
During the pendency of this action, Kassandra and Nicholas have remained in the care and custody of the Savages, apparently under an arrangement with K.E.S.I.L.
ASSIGNMENTS OF ERROR
The Savages assert that the Court of Appeals erred (1) in rejecting the factual finding of the county court that Gomez was unfit; (2) in holding that §§ 43-104.02 through 43-104.06 create jurisdiction to terminate parental rights in adoption cases for only those unwed fathers who file their notices of paternity with DSS within the prescribed 5 days of the birth of the child; (3) in refusing to apply §§ 43-104.02 through 43-104.06 to Gomez’ request for custody when Gomez himself sought relief under those statutes; and (4) in ordering that the children be immediately restored to Gomez, thus denying the children the protection of Neb. Rev. Stat. § 43-111.01 (Reissue 1993), applicable when an adoption is denied.
Gomez challenges the constitutionality of § 43-111.01 when applied to a father who has established a parental bond with his children, because Gomez asserts that the statute ignores the parental preference doctrine.
STANDARD OF REVIEW
Statutory authority to exercise subject matter jurisdiction may *918be raised sua sponte by a court. Jones v. State, ante p. 158, 532 N.W.2d 636 (1995); State ex rel. Grape v. Zach, 247 Neb. 29, 524 N.W.2d 788 (1994); Scherbak v. Kissler, 245 Neb. 10, 510 N.W.2d 318 (1994).
ANALYSIS
In the biblical tale of King Solomon, when two women argued over a baby, Solomon ordered the child cut in two. Solomon knew that the woman who begged for the baby’s life was the true mother and gave her the baby. “When all Israel heard about the decision the king had rendered, they respected the king because they saw that the wisdom of God was in him to administer justice.” 1 Kings 3:28. Solomon’s decision was not constrained by statutes and precedent. In Nebraska, the matter of adoption is statutory, and the manner of procedure and terms are all specifically prescribed and must be followed. Kellie v. Lutheran Family & Social Service, 208 Neb. 767, 305 N.W.2d 874 (1981); In re Petition of Ritchie, 155 Neb. 824, 53 N.W.2d 753 (1952).
Our analysis is controlled by the adoption statutes codified at chapter 43, article 1, of the Nebraska Revised Statutes. We note that these statutes have been substantively changed by 1995 Neb. Laws L.B. 712, but the changes are not applicable to this case. We hold that the adoption petition failed to comply with adoption statutes and therefore the county court lacked authority to exercise its subject matter jurisdiction over the proceeding.
In summary, our analysis begins with the premise that consent of a biological parent to the termination of his or her parental rights is the foundation of our adoption statutes. Section 43-104(3) provides that no adoption shall be decreed unless the adoption petition is accompanied by the consent of both parents, if living, unless the need for parental consent is rendered unnecessary by certain exceptions. Section 43-102 mandates that when an adoption petition is filed, all consents required by § 43-104 must be attached to the petition. Neb. Rev. Stat. § 43-105 (Reissue 1993) states that when parental consent cannot be given as provided in § 43-104(3), substitute consent shall be given by the guardian or guardian ad litem of the child. The Savages’ petition to adopt the children was not accompanied *919by Gomez’ consent or a substitute consent executed by the guardian ad litem. The lack of these consents is a jurisdictional defect which precluded the county court’s power to exercise its authority over the adoption proceeding.
At a hearing on January 28, 1993, regarding Gomez’ motion in opposition of adoption and request for custody, Gomez challenged the Savages’ petition for the reasons that the required consents from DSS were lacking. There is no record regarding the outcome of this challenge. However, parties cannot confer subject matter jurisdiction upon a judicial tribunal by either acquiescence or consent, nor may subject matter jurisdiction be created by waiver, estoppel, consent, or conduct of the parties. In re Interest of J.T.B. and H.J.T., 245 Neb. 624, 514 N.W.2d 635 (1994); Scherbak v. Kissler, 245 Neb. 10, 510 N.W.2d 318 (1994); Rohde v. Farmers Alliance Mut. Ins. Co., 244 Neb. 863, 509 N.W.2d 618 (1994).
Section 43-102 demands that certain consents or substitute consents be filed with the adoption petition.
[A]ny person . . . desiring to adopt a minor child . . . shall file, in the county court... a petition for adoption, signed and sworn to by the person or persons desiring to adopt, together with the consent or consents required by section 43-104 . . . and the certificates required by sections 43-104.02 to 43-104.06 or the documents required by section 43-104.07.
Section 43-104(3) provides that consent to an adoption is required from
both parents if living ... of a child born in lawful wedlock, or, subject to sections 43-104.02 to 43-104.06, the mother of a child born out of wedlock, except that consent shall not be required of any parent who (a) has relinquished the child for adoption by a written instrument, (b) has abandoned the child for at least six months . . . (c) has been deprived of his or her parental rights to such child by the order of any court of competent jurisdiction, or (d) is incapable of consenting.
When a biological parent’s consent is not required by § 43-104(3), the prospective adoptive parents must obtain substitute consent. Section 43-105 states that
*920when consent cannot be given as provided in subdivision (3) of section 43-104, consent shall be given by the guardian or guardian ad litem of such minor child appointed by a court, which consent shall be authorized by the court having jurisdiction of such guardian or guardian ad litem.
The Savages filed their petition to adopt the children in the county court on October 20, 1992. The relinquishment documents signed by Bechtold were attached to the petition as exhibits “A” and “B” and were incorporated by reference. The Savages’ petition stated that the relinquishment documents contained authority for K.E.S.I.L. to authorize the adoption. Also attached to the petition were two consents to the adoptions executed by K.E.S.I.L. No consents from Gomez or substitute consents were attached to the Savages’ adoption petition.
A court must give effect to the purpose and intent of the Legislature as ascertained from the entire language of the statute considered in its plain, ordinary, and popular sense and, if possible, discover the Legislature’s intent from the language of the statute itself. In re Interest of Powers, 242 Neb. 19, 493 N.W.2d 166 (1992). With the plain language of §§ 43-102, 43-105, and 43-104.04 before us, we must hold that the Savages’ failure to file Gomez’ consents or substitute consents with their adoption petition is a procedural defect that is jurisdictional in nature. This result is also indicated by prior decisional law.
In Klein v. Klein, 230 Neb. 385, 431 Neb. 646 (1988), a custodial father filed an application in a dissolution action, seeking a district court’s consent to the adoption of his child by his new wife for the reason that the birth mother had abandoned the child. The district court’s consent to the adoption was required under § 43-104(2) because it had jurisdiction over the child by virtue of the divorce proceedings. The birth mother appealed from the order of the district court granting its consent to the adoption, and the issue was raised regarding whether her appeal was from a final or an interlocutory order.
In Klein, we stated that the district court’s order granting consent to the adoption permitted the county court to entertain the adoption proceedings. In Smith v. Smith, 242 Neb. 812, 497 *921N.W.2d 44 (1993), we again stated that a district court’s consent to an adoption is needed under § 43-104(2) and that the lack of the district court’s consent prevents the county court from taking jurisdiction over the case. Without requisite consents, a county court lacks authority, or jurisdiction, to entertain an adoption proceeding. This conclusion is consistent with our analysis in Hiatt v. Menendez, 157 Neb. 914, 62 N.W.2d 123 (1954). In Hiatt, we stated that an irregularity and a failure of compliance with the statutory requirements of a proper petition for adoption may defeat the jurisdiction of the county court. See, also, Decoste v. City of Wahoo, ante p. 463, 534 N.W.2d 760 (1995) (holding that statutory prerequisites must be met before court exercises its subject matter jurisdiction).
Section 43-104 states that no adoption can be decreed unless the petition is accompanied by consents or relinquishments which indicate that parental rights have already been extinguished. The fact that the statute is phrased in the past tense indicates that the requisite consents should be obtained prior to filing the petition.
It may be argued that Gomez’ consent to the adoptions was not needed because the children were born out of wedlock and he failed to timely claim paternity under the provisions of §§ 43-104.02 through 43-104.06. In essence, those sections provide that a father of a child born out of wedlock may prevent an adoption from proceeding with the mother’s sole consent only if he files a notice of intent to claim paternity within 5 days of the child’s birth. In fact, the Savages’ adoption petition stated that
a notice of intent to claim paternity has been filed with the Nebraska Department of Social Services by a Martin Gomez claiming paternal rights to the minor children herein involved. The claim of paternity should not be recognized by the Court pursuant to the provisions of Section 43-104.02 for the reason that such claim is barred by not having been filed within five (5) days after the birth of each of the children, the claimant having at all times full knowledge of the birthdays of each of said children.
We have previously held that the 5-day filing requirement is *922not applicable to a father whose child is no longer a newborn, who has already established strong ties, and who has acknowledged and supported the child. In re Application of S.R.S. and M.B.S., 225 Neb. 759, 408 N.W.2d 272 (1987). We need not, indeed cannot, decide whether Gomez is such a father because we hold that substitute consent must have been obtained even if Gomez was subject to the provisions of §§ 43-104.02 through 43-104.06.
The allegations in the Savages’ petition that Gomez’ consent was not required because he had not filed notice of intent to claim paternity within 5 days of his children’s births are questionable substitutes for the statutory requirement that an adoption petition be filed with the requisite consents. Although it is true that an unwed father’s consent is not needed if he fails to claim paternity under § 43-104.02, § 43-104.04 states that
the Department of Social Services shall supply, a certificate that no notice of intent to claim paternity has been filed with the department and the filing of such certificate pursuant to section 43-102 shall eliminate the need or necessity of a consent or relinquishment for adoption by the natural father of such child.
No such certificate was filed with the Savages’ petition. Therefore, the county - court also lacked jurisdiction for this reason.
The consent filing requirements imposed by § 43-102 are not mere procedural matters which can be easily disregarded or waived. Children are not legally free for adoption unless both biological parents consent or one of the statutory exceptions to the need for their consent has been met. As a practical matter, there is little sense in filing a petition to adopt a child unless there is good reason to believe that the adoption can proceed. Section 43-102 ensures that prospective adoptive parents gather the necessary consents before filing their petition.
CONCLUSION
The county court lacked statutory authority to exercise subject matter jurisdiction to entertain this proceeding because Gomez’ consent or its substitute was lacking.
When a lower court lacks the authority to exercise its subject *923matter jurisdiction so as to adjudicate the merits of a claim, issue, or question, an appellate court also lacks the power to determine the merits of the claim, issue, or question presented to the lower court. County of Lancaster v. State, 247 Neb. 723, 529 N.W.2d 791 (1995); In re Interest of J.T.B. and H.J.T, 245 Neb. 624, 514 N.W.2d 635 (1994).
A judgment entered by a court which lacks subject matter jurisdiction is void. It is the longstanding rule in Nebraska that such a void judgment may be raised at any time in any proceeding. Bradley v. Hopkins, 246 Neb. 646, 522 N.W.2d 394 (1994); VonSeggern v. Willman, 244 Neb. 565, 508 N.W.2d 261 (1993).
Our disposition of this case makes it unnecessary to address the issue of the validity of Bechtold’s relinquishments, the standing of the Savages, the authority of the county court to terminate parental rights in adoption proceedings, and the parties’ assignments of error.
We vacate the orders terminating parental rights and placing custody in K.E.S.I.L. The cause is remanded to the Court of Appeals with directions to remand to the district court for further remand to the county court for dismissal.
Remanded with directions to dismiss.