AJ McLean has recalled how he once helped Aaron Carter check into rehab.

In a clip from the upcoming Aaron Carter: The Little Prince of Pop documentary obtained by People, the Backstreet Boys singer - who starred in the boyband alongside Aaron's brother Nick Carter - discussed the time the late popstar called on him for advice.

"(In) 2017, Aaron reached out to me, asked me for help. I said, 'Look, if you get on a plane, come out to L.A., I will make sure you get into treatment.' And he showed up. I was shocked, but I was happy, and he checked into a treatment centre in Malibu," he recounted. "A couple days later, I talked to him, and then he kind of went off the map. I think it was maybe two weeks, so I called my friends at the treatment centre, and they said he checked himself out."

Aaron struggled with substance abuse and mental health issues over the course of his life. He was found dead at his home in November 2022 at the age of 34, with a coroner reporting that he had accidentally drowned as a result of gas and drug effects.

Elsewhere in the footage, AJ referred to his own past with drug and alcohol addiction. Following a relapse in late 2019, the performer has remained sober ever since.

"I was a functioning addict. I had been in and out of the rooms since 2001, so for 22 years I've been battling my own s**t," the 45-year-old explained. "I almost lost my marriage, I almost lost my band, I almost lost my life. The last time I relapsed, which would be 18 months ago, my youngest daughter was kind of the nail in the coffin for me. She said I didn't smell like her dad. That was enough. That pretty much did it for me and I have stayed sober since and I plan on staying sober. It's a daily thing."

Aaron Carter: The Little Prince of Pop will begin streaming via Hulu on 1 May. The project will also include interviews with his ex-fiancée Melanie Martin and friend Taylor Helgeson.