98 Degrees' Jeff Timmons Says Impossible to Prepare for Boy Band Pitfalls, Fame

Liam Payne's death is putting a spotlight on the unseen struggles teen singers face when they put trust into stardom, even when it seems like they're thriving ... according to Jeff Timmons from 98 Degrees.

Jeff is just one of several boy banders opening up about the rollercoaster ride his group, Backstreet Boys, *NSYNC, New Edition, New Kids on the Block and many others endured for decades. They're all featured in the new Paramount+ documentary, "Larger Than Life: Reign of the Boybands."

On Tuesday's "TMZ Live," Jeff told us the sudden fame they all encountered -- mostly in the early 2000s -- was absolutely a blessing, but it was also impossible to prepare for everything that was thrown at them.

He says 98 Degrees shared stages with Liam and One Direction, as well as The Wanted, back when the young acts were starting to blow up ... and he was surprised at how well-adjusted the guys were so early in their careers.

He attributes part of that to the rise of social media scrutiny, but also noted you never "know what goes on behind closed doors" -- hinting at the potential pitfalls of substance abuse ... with which Liam struggled at times.

The documentary covers those issues and several other challenges and triumphs for everyone from The Beatles to Bell Biv Devoe and Hanson -- and Jeff proudly adds he and the 98 Degrees crew are still doing it ... performing live and recording new music.