When a party has issues with the custody or visitation of a child, those issues are usually adjudicated by the same judge that handles their divorce. However, when it comes to adult disabled children, the issues are more complicated.
Section 513.5 of the Illinois Marriage and Dissolution of Marriage Act (IMDMA) allows a parent to file a motion asking for the support of a disabled child. However, there is no provision in the IMDMA that would allow for the adjudication of visitation or allocation of parental responsibilities and parenting time of an adult disabled child. Instead, those provisions are incorporated into the Probate Act of 1975.
The Probate Act specifically sets out definitions of who would qualify as a disabled person and would therefore be entitled to its benefits. If your child meets the definition of a disabled child pursuant to the Probate Act, then you would file a Petition for Guardianship of said child. If you and your spouse have already been designated as co-guardians of an adult disabled child, you will need to first seek to modify the co-guardianship in probate court and adjudicate any visitation issues with the probate court. If your child is not yet an adult, your divorce judge will be able to address custody and visitation issues but only until the child emancipates.
Once the guardianship and visitation issues have been settled in probate, a divorce judge would be able to address issues regarding the support of the adult disabled child, as well as any other pending issues in your divorce.