Nicki Minaj's New Boyfriend is a Rekindled Ex-Flame

Nicki Minaj has a long history with her new boyfriend, because she first fell for him when she was a teenager -- and she feels he's changed since his checkered past.

Sources close to Nicki tell TMZ ... her first relationship with Kenneth Petty happened when she was a 16-year-old living in Queens, and she calls him one of her first loves. As they say, what's old is new again ... she's been showing him off in pics from a romantic getaway for her 36th birthday.

We're told Nicki understands Kenneth has a troubled past -- he's a registered sex offender convicted of attempted rape -- but she's confident he's matured since his time in NY state prison in the late 1990s. Nicki believes in second chances and has faith he'll be good to her.

As we reported ... Petty was convicted of first-degree attempted rape in April 1995, when he and his victim were both 16. Sources close to Nicki say the full context of the crime is Kenneth was dating the victim -- and her mother filed the charges because she didn't approve of him.

Our sources say Nicki and Kenneth still have great chemistry, despite all the years between their relationships. We're told she was very stressed out before they got back together, but she's much happier since rekindling their romance.