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. You must file a Temporary Restraining Order (TRO) with the court to petition the court for emergency custody of your children.Important Forms Regarding Child Custody in San Antonio. The below links provide useful free forms and guides pertaining to child custody in Bexar County. Call us at 210-987-9001 to discuss your unique situation and find out how we can assist you in modifying your child custody agreement. This guide tells you how to ask for a custody, visitation, child support, medical support, and dental support order. Submit a Petition: Fill out and submit the required forms to the court; Notify the Other Parent: Legally inform the other parent about the modification request. In general, Texas has very few official legal forms. If not, you may need to file a Petition to start up a proceeding so yo have somewhere to file your agreement. This form tells the court what your case is about and what you want the court to do.