Disney Star Adam Hicks' Brother Behind Wheel in 2014 Deadly Crash

Disney star Adam Hicks' world was crumbling long before his arrest for armed robbery, due to his brother doing time, and his mother passing away ... TMZ has learned.

Adam's little brother, Tristan, was the driver in a 2014 car crash in Vegas that killed a 17-year-old girl. Police say she died after she was ejected from the car.

Tristan, who was 18 at the time, took off on foot. He was eventually arrested for fleeing the scene.

Sources tell us Adam had recently gone to Vegas to testify at his brother's parole hearing. Adam paid for Tristan's bail and most of his legal fees during the case.

Things went further south a year later when Adam's mother, Lucy, died unexpectedly from a heart attack. We're told Tristan's accident had weighed heavily on her.