This, despite their harsh words for each other in public since they broke off their engagement in March 2009, and a custody fight over their son, Tripp, now almost 18 months old.
The source says things have re-heated between Bristol, 19, and Levi, 20, now that Bristol's mother, former GOP vice presidential candidate and ex-Alaska Gov. Sarah Palin is on the road a lot, and Bristol has her own place. "They spend more time together than most people think."
The sourse adds, "Levi even stays overnight. I even think they are back together."
When Levi spoke to Maggie Rodriguez on "The Early Show" in October, it .
"We've talked," he told Rodriguez. "We don't talk like, you know, it's just like, 'Hey, how's the baby doing? Can I come pick him up?" '
In their custody battle, Bristol claims Levi "exercised sporadic visitation rights" and "wants the rights for his own self-promotion."
Some of that self-promotion included a nude photo shoot for Playgirl magazine.
There were also harsh words for the Palin family in that interview with Rodriguez, with Johnston saying, "They threw me out there (on the presidential campaign trail), and then that came out that Sarah didn't really like me. Todd (Sarah's husband and Bristol's father), I knew Todd didn't like me, so they were kind of like backstabbing me."
The war of words .
In an appearance on the "Oprah Winfrey Show," Sarah Palin criticized the photo shoot. "I call it porn," she said. "It's kind of heartbreaking, the road he's on right now."
In an "Oprah" appearance of her own, Bristol said she wouldn't have sex again until she gets married, and urged other women avoid sex out of wedlock. She also advocated for teen abstinence in a public service announcement for the Candie's Foundation.
In February, a judge ordered Levi to pay his ex-girlfriend $18,500 in child support.
But now, says Us, the country's most famous unwed parents appear to be getting back together.
And in the interview with Rodriguez, Johnston hinted at his feelings toward Bristol, saying, "I do wish me and Bristol could hold a relationship and be -- you know -- raise the baby."