Section 610 provides for the modification of a child custody judgment upon a proper showing, and it goes without saying that the death of the custodial parent in this case constituted a change requiring a modification of the custody decree. (See Sholty v. Sholty (1966), 67 Ill. App.2d 60, 214 N.E.2d 15.) The fact that the respondent elected to proceed under the Probate Act of 1975, however, was not determinative of the court's power and did not serve to divest the court of its jurisdiction or its obligation toward the minor that arose in the dissolution proceeding. The instant court was not bound by the form of the proceeding initiated by the respondent, and it properly looked to the substance of the action before it in making its determination.

Similarly, the court in Soldner v. Soldner (1979), 69 Ill. App.3d 97, 102, 386 N.E.2d 1153, 1157, required that there be "convincing grounds" for custody to go to a nonparent. In Sholty v. Sholty (1966), 67 Ill. App.2d 60, 64-65, 214 N.E.2d 15, 17, the court said that "other circumstances" may in some cases be sufficient to overcome a parent's right to custody. Thus, we are faced with the question whether there were "convincing grounds," "compelling reasons," or "other circumstances" that justified the trial court in placing Christy with her half-sister instead of with her father.

Obviously the death of the parent having custody is a significant change in circumstances such that the custodial portion of the judgment would require modification. Sholty v. Sholty (1966), 67 Ill. App.2d 60, 214 N.E.2d 15. • 5 In its written order, the trial court directed that the judgment of divorce be modified and amended by awarding permanent custody to petitioners.

We believe, however, that even in absence of the statutory provisions to which we have referred, the death of the natural father in itself created a sufficient change of circumstance to permit a new inquiry as to whether Mrs. Banks was then fit to be vested with the custody of the minor child. Sholty v. Sholty, 67 Ill. App.2d 60, 214 N.E.2d 15. In the record before us, we note that Billie Banks has two children of a marriage prior to her marriage to Renie LeCocq; that, at the time of LeCocq's divorce from her, she was pregnant by one Ozzie Banks; that she subsequently married Ozzie Banks but that he left her when she was pregnant with the second of her two children; that Ozzie Banks left while the weather was cold and that she and her children (other than Edward who was in custody of his father) moved in with one Robert Williams, because there was no heat in the Banks' house.