The actor, who came to fame on The Famous Jett Jackson, died of a self-inflicted gunshot wound last August at age 29. He was diagnosed with bipolar disorder as a teen, and mother Velma Love tells WIS TV he experienced "some periods of sadness and that stabilized quickly."
"He would sometimes call me and say he was feeling a little sad again," sister Tamu Lewis adds. "It was always a quick recovery and I, too, feel that he was always concerned about us. He was always protective of us."
Young starred in Friday Night Lights in 2004, and appeared on Scrubs and Smallville in later years. The actor was a lead character on Rizzoli & Isles at the time of his death, and his mother and sister say he seemed to be doing better.
"After we knew that Lee was found dead in his apartment ... we, of course, were stunned," Love says. "I guess ['why' is] the question that everyone would ask. And we really don't know those answers and there's really no way to know."
Love and Lewis have launched the Lee Thompson Young Foundation in memory of the actor. The institution seeks to eliminate "the stigma associated with mental health conditions through education, literacy and youth programs."
"I do feel like someone like Lee impacted by [mental illness] and it being in the news ... kind of makes it okay. People know that Lee wasn't the only one," Lewis says. "For them to see everything he accomplished in the 29 years, it's more than some people accomplish in their whole lives. He was able to do that with a mental illness and, yes, it ended tragically but, through that we're inspired."
Rizzoli & Isles attributed Young's death to a car accident in the series, and honored the actor and his character Barry Frost in Tuesday night's episode.
Notable deaths of 2014 [PHOTOS]