Bristol reportedly breaks off engagement to Levi

Ex marks the breakup spot for Bristol Palin and Levi Johnston.

The 19-year-old mom called off her second engagement to her baby daddy last week following a fight over one of his ex-girlfriends, a source close to the couple tells E! News.

They must have been on pretty shaky footing already, because the thorn in Bristol's side wasn't even the ex who turned up pregnant this week, but some other girl!

While Lanesia Garcia was outed by the National Enquirer as Levi's possible second baby mama, our source—along with Levi's lawyer—insists that Garcia herself has admitted that the Playgirl poser is not the father of her unborn child.

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"Lanesia and Levi have dated off and on over the past few years but he's not the father of that baby," says the source. "Lanesia's other ex boyfriend is the father. She's not the reason [Bristol and Levi] broke it off."

Instead, it was Levi's other ex, Briana Plum, who put a hitch in Bristol's wedding plans.

"There was an interview with her and Bristol wasn't happy about some of the things said," the source tells E! News. "There was also some picture on Facebook of him and Briana and Bristol just said, ‘Let's hold off on the engagement.' "

Neither Paln nor Johnston have publicly commented on their latest split.

The parents of 19-month-old Tripp landed on the cover of Us Weekly last month with news of their rekindled romance and there was even talk about shopping a reality show featuring their young family.

Well, all that was never well probably won't end well the second time, either.