Bristol Palin and Levi Johnston Broke Off Engagement

The split happened "a few weeks ago," according to a source close to the couple, but it's unclear what precipitated it. "It was a mutual thing," adds the source. Bristol, the 18-year-old daughter of Alaska Governor Sarah Palin, spoke with FOX News in February and told Greta Van Susteren that she and Levi – who are parents to 2-month-old son, Tripp – expected to get married after they completed high school.

"It kind of just happened," says the source, referring to the split. "I thought they would stick it out. But I think they can work together to raise Tripp." "I'm not sure what caused [them to break up] – it's common knowledge," says another source who knows the family. Despite the breakup, Levi still sees the couple's son. Levi's dad, Keith Johnston, told PEOPLE recently that his son is a devoted and "proud father."