This page contains all of the Family Law court case forms that the Clerk's Office provides. These forms and instructions are available in the General Clerk's Office, Room 108, in the Nassau County.Petition for (Custody) (Visitation). After completing this form, you should sign the form before a notary public or deputy clerk. You should then file it with the clerk of the circuit court in the. A petition for custody would be filed in the juvenile, family, or domestic relations Court with jurisdiction over the child, at the county level. If you prepare your own petition, file it with the Clerk of Family Court on the 11th floor of the courthouse at. Fill out the Application for Modification of Court Order or Cross-Application for Modification of a Court Order. 1. Fill out your court forms. Follow these steps to change a parenting time, custody, or visitation order.