These forms and instructions are available in the General Clerk's Office, Room 108, in the Nassau County. Many forms in Texas are not available in a fillintheblank format.This guide includes forms and instructions for a letter and affidavit to request that the court register an out-of-state custody order in Texas. Court Initiated Guardianship Forms. A petition for custody would be filed in the juvenile, family, or domestic relations Court with jurisdiction over the child, at the county level. This guide tells you how to ask for a custody, visitation, child support, medical support, and dental support order. If you and your co-parent cannot reach an agreement on child custody without any help, you need to file a petition for child custody. Suits Affecting the ParentChild Relationship. In an uncontested case, parents agree on all terms. Step 2: Complete your forms.