Tristan Thompson has taken over as caregiver for his younger brother in the wake of his mom's death, and is now taking steps to make his guardianship official.
In legal docs, obtained by TMZ, Tristan's asking the court to become guardian of Amari Thompson. The documents state Tristan took over the responsibilities of care for 17-year-old Amari after their mother, Andrea, died in January.
The documents also state Tristan and Amari's dad, Trevor, has been absent from Amari's life -- leaving Tristan as his closest family member who is able to provide the care he needs.
Amari has several medical diagnoses that leave him unable to care for himself -- and Tristan will need to help him with his day-to-day as well as with his medical appointments.
What's more, the documents say Amari is set to receive approximately $103,475 as a result of Andrea's death ... and Tristan will protect that inheritance from loss or injury.