Texas allows relatives to file for custody only in limited circumstances where the natural parental relationship has failed, if the natural parents do not agree to appointment. This means that the parents must have died under Texas Family Code Section 153.431 or there has been an adjudication of unfitness, or neglect and abandonment of the child by the parents. In these situations, a relative may file a petition for custody in local county court, which will be heard by a court to determine if the petition is in the best interests of the child.
Obtain a blank copy of the Petition for Custody from the clerk's office of the courthouse in the county where your niece currently resides. Custody of a child, referred to as Conservatorship in Texas legal parlance, is the right to possession of a child, with the attendant rights to raise the child as the conservator sees fit. Include information about the natural parents, yourself and the procedural history to complete the petition. Include in the narrative section your basis for requesting custody. Be sure to complete and attach a case information sheet, a blank copy of which will also be available in the clerk's office.
If the natural parents agree to transfer custody to you, they must complete an affidavit of relinquishment which should be attached to the custody petition.
File your petition with the county clerk's office. You will receive a stamped copy with a status date on your petition which you must serve upon the natural parents by using a special process server such as the county sheriff. Texas courts prefer the parties to reach amicable agreements, but will set the matter for a contested hearing on the merits if no agreement can be reached.
Appear at the hearing on your petition. Texas courts are guided by the best interests of the child in making custody determinations, and will inquire into your financial, personal, and criminal background in deciding if vesting custody in you is in the child's best interests.