4. SIENNA MILLER
When: 2001, July 2005
According to the rumor mill, Miller wanted to rekindle her and Bloom’s brief 2001 romance after her split from Jude Law in 2005. The two were seen around London together trying to reignite what they once had. Their previous romance happened before their respective rises to fame, when Miller was only 19.
Smash Probability: We know it happened the first time, and dudes always cheat on their girlfriends with their ex-girlfriends, so the second time seems plausible, too.