Do you have an attorney yet? Since she has custody of one child already, judges are extremely reluctant to separate siblings. Regardless of psychiatic problems, you would have to provide overwhelming evidence she is a threat to the child's well being. It will probably need to be powerful enough, where the state is actually taking the other child away at the same time. Plus, with you being the primary wage-earner, and her at home, it will be a tremendous uphill battle, as she will be the presumed primary parent. Illinois also uses the presumption that kids should live primarily with one parent, thus they will not award shared parenting if you have a custody battle. What is your wife's view on this? Is she voluntarily willing to give up custody? Direct negotiation is going to be your best bet. Gigi gave you a breakdown of how things will be split in the property settlement in the previous post, and it appears very accurate.