This is an appeal from a circuit court order denying a motion to change custody of minor children. Concluding that there was insufficient evidence to allow the trial court to make a meaningful determination as to the best interests of the children, we reverse and remand for further proceedings.
FACTS
Sandy K. Williams (Mother) and Barney D. Williams (Father) were married on September 24, 1977. Bom to that union were two daughters, whose present ages are nine and ten. The marriage was terminated by a judgment and decree of divorce dated January 20, 1983. This divorce decree, which determined that both parties were fit parents, approved an agreement of the parties wherein the “physical and residential care” of the children was given to Mother “with parental access and parental rights of hearing” to Father.1 Father was required to pay monthly child support in the amount of $150 ($75 per month per child).
Subsequent to the divorce, Father failed, neglected or refused to pay the child support required of him. After an order to show cause hearing in October, 1984, the court found him to be $2800 in arrears, held him in contempt and ordered that the support obligation be increased to $175 monthly, with $25 to apply towards the arrearages. At some later time, under SDCL 25-7A-22, Mother sought an increase in support from the Department of Social Services (DSS). After a hearing on that request, the DSS hearing officer, on December 5, 1986, denied the requested increase, continued the $150 per month payment previously ordered by the circuit court and noted that if Father again became delinquent, Mother could proceed to obtain an “Order of Withholding.” Although the record is silent as to the specifics, it does appear that Father continued to be delinquent and other proceedings were conducted, since in his testimony in the current proceedings he testified that the support was being withheld from his paycheck by his employer.
In August, 1987, Father filed a motion seeking custody of the children. In affidavits regarding the motion, the parties made various serious allegations against each other.
The trial court conducted an evidentiary hearing on the motion on August 27, 1987. During Father’s case-in-chief, he testified and, through his attorney, conducted an adverse examination of Mother. The only other witness was a former boyfriend of Mother. At the close of Father’s evidence, Mother’s counsel, “reserving the right to call some witnesses,” moved for dismissal. That motion was granted and the trial court later entered a written order denying change of custody and allowing Father “reasonable” visitation rights. This appeal followed.
DECISION
As is too often the case in actions such as this, the parties concentrated more on demeaning each other’s conduct than they did in addressing the real issue, namely the best interests of the children. As will be alluded to later, they placed the trial court *392in the position of attempting to ascertain which parent is “the least worst.”
Mother’s conduct was clearly flawed. Her character and fitness as a parent are obviously tarnished by the following: she has lived with and/or had sexual relationships with a number of men while the children were in the home; two of these boyfriends were convicted felons (one for burglary and another for dealing in drugs); one of her live-in boyfriends abused her, often in the presence of the children, yet she continued to reside with him after the abuse; she has admitted to abusing the children, including kicking them and on one occasion blackening both eyes of one of the daughters; she has neglected the children by occasionally leaving them unattended, even while they were ill; she relied heavily upon the Boys and Girls Club to help raise the children by having them go there daily after school, even to the extent of sometimes eating meals there; she has had a very transient existence, having lived in twelve different residences in four cities including Aberdeen, Sioux Falls, Chelsea, and currently in Hill City, South Dakota.
By the same token, Father’s conduct has been far from exemplary. Among other things, he did not pay child support. Even were we to accept his argument that Mother had agreed (prior to the divorce) to waive support in order to get the kids, his conduct cannot be excused or condoned, morally, legally or in any manner, especially in view of the record before us. Further, just as Mother had a remedy to collect support, he had a remedy to have it modified, which he never attempted. He attempts to excuse his delinquencies by virtue of the extensive visitation he exercised; however, that visitation period is identical to that which was considered and provided for in the original decree of divorce.
Additionally, Father himself had a “live-in” girl friend, who he now plans to marry. The fact that she no longer lives in the home (and will not until after their marriage) does little to minimize his indiscretion. It was clearly established that she moved out shortly before the modification hearing in order to make him look better to the judge. Nonetheless, since Father has maintained his employment with one employer and has purchased and remodeled a house, he could perhaps provide the more stable environment for the children.
Unfortunately, there was no testimony offered from the children or from disinterested persons relating to the well-being of the children or their best interests. No testimony was offered from any teachers, social workers, babysitters, personnel of the Boys and Girls Club or the grandparents. There was no homestudy conducted by DSS or any other social agency.
The trial court was obviously frustrated by the state of the record, as evidenced by its statement at the close of the hearing, as follows:
Well, here’s the situation in my mind: both parents have exhibited immoral conduct.
Now, so I don’t have to start equating whose immorality is higher than the others — that’s sometimes hard to do — can you be immoral with one person or does it take more than one person to be immoral with? Now, she’s got, apparently in numbers, more than the defendant. Starting on that premise they’re both immoral, I think that’s pretty well stated, and probably the children should be taken away and put in a foster home, but there’s no dependency and neglect proceeding in front of the Court so I can’t do that. So I’ve got to put the children in an immoral home either way I go. So on that premise, then, we go to the other area, which is, she moved sixteen times in so many years.
But I have to equate that with something else; and that is that economics has a lot to do with where you go and why you stay. The testimony has been, it’s unre-futed that he didn’t pay his child support, so she was in financial problems with the two children. So I really don’t see where there’s that much change. There's been no showing except for this one incident where the children have two black eyes, and she’s admitted to that but there’s been nothing else; that they’re in jeopardy, or that they would be in better hands *393with the father. So I feel that there has not been substantial evidence presented to this court that I should change custody-
irrespective of whether we agree or disagree with the trial court’s characterization of the “immoral” conduct, we believe it missed the point, namely what is truly in the best interests of the children.
We must start from the basic premise that when a divorce decree is based on an agreement of the parties, the issue of custody may be considered in a subsequent custody modification hearing without the “substantial change of circumstances” constraints. Hansen v. Hansen, 327 N.W.2d 47 (S.D.1982); Kolb v. Kolb, 324 N.W.2d 279 (S.D.1982). Thus, the party seeking modification must show that the best interests and welfare of the children requires a change of custody. Flint v. Flint, 334 N.W.2d 680 (S.D.1983); Kolb, swpra. In our review, we must ascertain whether the trial court has clearly abused its discretion. Flint, supra; Hansen, supra; Kolb, supra; SDCL 25-4-45. However, the trial court’s exercise of discretion is not uncontrolled and must have a sound and substantial basis in the testimony. Kester v. Kester, 257 N.W.2d 731 (S.D.1977).
Considering the state of the record, we conclude that Father has met his prima facie burden of proof and therefore the trial court abused its discretion in concluding that the children’s best interests required that they remain with Mother. Even if Father’s relationship with his fiancee is characterized as immoral, immoral conduct per se does not make him unfit to have custody. Spaulding v. Spaulding, 278 N.W.2d 639 (S.D.1979). Not only are Mother’s elicit relationships more serious, Rivers v. Rivers, 322 N.W.2d 864 (S.D.1982); Spaulding, supra, but the frequent moves and transient lifestyle, as well, are not in the children’s best interests. Jasper v. Jasper, 351 N.W.2d 114 (S.D.1984). Nor can we condone Mother’s exposing the children to men of questionable character, to-wit: two convicted felons and one physical abuser. Further, despite the trial court’s comments, we must add that there is nothing in the record to support the fact that Father’s unexcused failure to pay child support in any manner influenced Mother’s transient lifestyle or other conduct.
Counsel, in cases such as this, have an obligation to establish by appropriate means that the best interests of the children are served by placing them with their client. Although presenting a prima facie case, Father’s counsel did not fully fulfill that obligation because his principal reliance was on the testimony of the parties. However, in these important cases, when trial lawyers fail to fulfill this obligation, trial courts, in their role of parens patriae of the children, must insist that more be done. As stated in Jasper: “It is the trial court’s duty to see that the children are protected at every turn ... The parents’ personal wishes and desires must yield to what the court in the discharge of its duty regards as the children’s best interest.” 351 N.W.2d at 117 (citations omitted). At the very least, trial courts have the authority, and at times the obligation, to require a homestudy of both parents, so it can be assured that the children are not placed, or do not remain, in surroundings seriously detrimental to their well-being. See Garnos v. Garnos, 376 N.W.2d 571 (S.D.1985); Karim v. Karim, 290 N.W.2d 479 (S.D.1980). In addition, the court may, in its discretion, call and interrogate witnesses. Haugen v. Haugen, 82 Wis.2d 411, 262 N.W.2d 769 (1978); SDCL 19-14-26 and 19-14-27.2
We therefore reverse and remand this case to the circuit court for further proceedings consistent herewith.
WUEST, C.J., and MORGAN, J., concur. *394SABERS, J., concurs in result. HENDERSON, J., concurs in result in part and dissents in part.. In the decree, the court specified several provisos, including that: father would get "extremely reasonable and liberal visitation rights”; father would have visitation two nights during each week during the evening hours; father would have visitation on alternating weekends and various holidays; father should receive continuous six weeks’ summer visitation (which he never exercised); neither would move out of the City of Aberdeen without first giving sixty days advance written notice by certified mail and if the parties could not reach a voluntary agreement concerning change of residence the matter would be submitted to the court; the parties would consult with each other frequently in an attempt to mutually agree regarding the general health, welfare, education, and development of the children; they would not attempt or condone any conduct or action to estrange the children from the other party; they would encourage and foster respect and affection in the children for both parents; they would keep each other advised as to any serious illness or other major development with respect to the children; they would keep each other advised of each other’s residence and business address and whereabouts on vacation.
. SDCL 19-14-26 provides: “The court may, on its own motion or at the suggestion of a party, call witnesses, and all parties are entitled to cross-examine witnesses thus called.” SDCL 19-14-27 provides: “The court may interrogate witnesses, whether called by itself or by a party. This power shall be used sparingly and only when the interests of justice require.”