R. Kelly absolutely knew Aaliyah was a minor when he married her in 1994 ... that's according to his former tour manager who now says he unwittingly and regretfully helped it happen.
Demetrius Smith has admitted he helped get the fake ID for Aaliyah the day before her wedding to Kelly -- but on "TMZ Live" Thursday he told us the marriage was the last thing he wanted to see go down.
On the heels of Kelly pleading not guilty to the fake ID allegation, Smith told us he actually wanted to delay the singer from walking down the aisle with Aaliyah ... who was only 15 at the time. Smith claims his intent was to "buy time" until he came up with a better plan to convince Kelly NOT to marry her.
Smith says both he and Kelly knew she was underage. Interestingly, he says the ID he had made for Aaliyah did NOT have an age on it. He would not elaborate on what kind of ID it was.
Smith says his hindsight is 20/20 -- and he told us how he wishes he'd handled Kelly and the fake ID back then. As for testifying against Kelly in court ... he'll do it, but as he's previously said, he doesn't want Kelly to rot in prison.