On December 6, 1976, Jacqueline Jarrett (W) received a divorce from Walter Jarrett (H) in the circuit court of Cook County on grounds of extreme and repeated mental cruelty. The divorce decree, by agreement, awarded W custody of the three Jarrett children subject to the father's right of visitation at reasonable times. Seven months later, alleging changed conditions, H petitioned the circuit court to modify the divorce decree and award him custody of the children. The circuit court granted his petition subject to the W's right of visitation at reasonable times, but a majority of the appellate court reversed, and we granted leave to appeal. H and W had three daughters, who, at the time of the divorce, were 12, 10 and 7 years old. Five months after the divorce, W informed H that she planned to have her boyfriend, Wayne Hammon, move into the family home with her. H protested, but Hammon moved in on May 1, 1977. W and Hammon thereafter cohabited in the Jarrett home but did not marry. At the rehearing, H testified that he thought W's living arrangements created a moral environment which was not a proper one in which to raise three young girls. He also testified that the children were always clean, healthy, well dressed and well-nourished when he picked them up and that when he talked with his oldest daughter, Kathleen, she did not object to W's living arrangement. The circuit court found that it was 'necessary for the moral and spiritual well-being and development' of the children that H receive custody. In reversing, the appellate court reasoned that the record did not reveal any negative effects on the children caused by W's cohabitation with Hammon and that the circuit court had not found Jacqueline unfit. It declined to consider potential future harmful effects of the cohabitation on the children.