Tristan Thompson is seeking sole conservatorship of his 17-year-old brother Amari. The NBA star's brother is confined to a wheelchair due to Lennox-Gastaut syndrome, a severe form of epilepsy. Their mother Andrea Brooks died last January and she was the sole legal guardianship of Amari since 2014. According to Entertainment Tonight, their father can not be located.

“I have not had any contact with him since his separation from our late mother in 2014, and contact was minimal prior to that date,” Tristan said of his father in legal documents obtained by the publication. “My only contact with Trevor Thompson in the past nine years was a brief interaction when he appeared at my mother's funeral. I have no knowledge of his current or recent whereabouts.”

The athlete said he seemed legal counsel to track down his father “but they were unable to obtain any information about Trevor's current location or other relevant details.”

Tristan's father has been away from the family since the 2014 separation between him and his late mother. Andrea died at age 53 of a heart attack. She lived in Toronto.

“Since then, Trevor Douglas Thompson has effectively abandoned the proposed ward; he failed to pay any child support despite the court order and has not been in contact with the proposed ward or Andrea Marie Brooks since July 2014,” the court documents state per the outlet. “He has done nothing to support or raise the proposed ward since then and has relinquished all rights to have any say in the proposed ward's care.”

Back in September, Tristan was awarded with temporary custody of his brother. It allowed the athlete to have “all the powers a parent having legal custody of a child would have, such as managing Amari's finances, traveling with him both in the U.S. and internationally, applying for American citizenship, deciding living arrangements and obtaining legal counsel.”

After the death of his mother, Tristan and Amari stayed with ex Khloé Kardashian as his home was being fixed.

Tristan thanked her family for helping him during the difficult time.

“Thank you so much — especially for me and my family — I don’t know what I would do without you guys,” he told Khloé, Kim Kardashian and Kris Jenner. “You guys are so busy and have so much going on, I just hope I can continue blessing you guys with everything my mom would want for you.”

Khloé and Tristan share two children together: daughter True and son Tatum. Tristan also has son Prince Oliver with ex Jordan Craig and son Theo with Maralee Nichols.