What happens in Vegas doesn't always stay in Vegas -- especially when two people with famous relatives get married to each other following an epic night out!

The unlikely union between Clint Eastwood's daughter and Jonah Hill's brother doesn't have a happy ending, though. Francesca Eastwood, 20, is seeking an annulment from Jordan Feldstein a week after their impromptu nuptials at a Las Vegas wedding chapel.

TMZ reports today (Nov. 25) that the model-actress is seeking the dissolution of her quickie marriage to Feldstein, who manages music acts such as Adam Levine, Maroon 5 and Robin Thicke.

The pair wed following "a wild night in Vegas," a source tells Us Weekly, adding they "were drinking a lot!"

Not very surprising. Another source confirms that the twosome "didn't know what they were doing."

Eastwood, who appeared in the reality show 'Mrs. Eastwood & Company,' most recently dated celebrity photographer Tyler Shields.