Petition for (Custody) (Visitation). Child Support, Visitation, Custody and Paternity Petition Forms.Where to File for Custody. Custody cases are usually started in Family Court. Complete General Form 17 to petition for custody or visitation. Packets of forms are available for sale to be used in filing a new case or modifying a case in either the Family or Civil courts. To get or change a court order for custody or visitation, you must file forms at the Clerk's Office at the Lamoreaux Justice Center. Fill out the form called Response to Petition for Custody and Support for Minor Children (form FL-270). 1. Fill out a child support modification petition. 2. File the petition with the Family Court that most recently established your order. 3.