One of hip hop’s longest running mysteries may be solved – and it’s a pretty B.I.G. deal.

A high school senior who grew up in the Bronx says he’s that chubby-cheeked kid on the cover of “Ready to Die” – the acclaimed debut album by slain rapper, Notorious B.I.G.

“Every time people find out they ask me if I got a lot of money out of it,” Keithroy Yearwood, 18, told the Daily News.

He didn’t.

He made only $150 for the two-hour modeling agency shoot, where he was shot in diapers, sporting a neatly picked-out Afro.

Released in 1994 by Sean (Diddy) Combs’ Bad Boy Records, “Ready to Die” sold 3.3 million copies, according to Nielsen SoundScan.

“I just want people to know that’s me,” Yearwood said. “The truth is finally coming out.”

Fans, who observed the 14th anniversary of the rapper’s death on March 9, have wanted to know the truth for years. Many speculated it was an early photo of B.I.G. (his real name was Christopher Wallace) or one of his kids. Others thought it might be one of Diddy’s kids.

No one was sure – not even the graphic designer of the album, Cey Adams. “That ended up being one of the most-asked questions of all-time,” said Adams, who thought the baby was the son of a hairstylist that worked at the record label.

Butch Belair, who took the famous photo, also thought the baby was related to someone close to the project.

“It was a friend of someone’s friends’ kid who had this cool Afro,” the photographer said. “The Afro was as big as he was.”

When RapRadar, a popular hip hop website, asked Combs about it last year, he said,

“That was a baby we just found ….We did a little casting for somebody that looked like Big.”

Diddy’s record company couldn’t confirm that Yearwood is the cover star saying, “files from then would be hard to find.” They did confirm the baby came from an agency.

Yearwood’s mom Delcenia Burns, 43, took out stacks of baby pictures of her son at their Sussex County, N.J., home to show he’s one and the same – and dug up papers from the child modeling agency Chicky’s Kids to support her son’s claim. The agency, now closed, sent her and her then-infant camera ham to the casting, she told The News.

Burns said it was tough to get her son gigs because of his full head of hair. Some potential jobs even wanted to pose him as a girl, his mom recalled.

This time, the Afro worked in his favor.

“We got a call from the agency saying he got the job,” Burns said. “We still didn’t know how big this was going to be.”

It was years before Yearwood was able to appreciate the sheer magnitude of his place in hip hop history. All his relatives had posters with the album cover on their walls but it wasn’t until he was 8 that it all sunk in.

“When I first found out about it, it wasn’t a big deal to me,” said Yearwood, who hopes to be a basketball star and study sports management in college. “Now, of course, it’s a big deal to me.”

Yearwood, whose favorite B.I.G. songs are “Juicy” and “Big Poppa,” insists he doesn’t discuss the album much because most people don’t believe him. But, he admits:

“It’s an honor to be on this album.”