Actor Robert Downey Jr., who battled drug addiction for years before getting sober in 2002, has stepped forward to help his son Indio who was arrested for cocaine possession last month.

The 20-year-old, a musician, struggled with substance-abuse issues in the recent years. He voluntarily checked himself into rehab after the arrest, people.com quoted a source as saying.

"Robert clearly understands the struggle, and while of course this relapse was very upsetting to him, he is very proud of his son. Indio truly wants to stay clean, and no matter what, his dad will be right there with him," added the source.

Indio has the support of his mom, Deborah Falconer, who was divorced from Downey in 2004, and his step mom, Susan.