Celebrity Cheaters! From Kristen Stewart to Ashton Kutcher: 11 Stars Who Couldn't Keep It in Their Pants (PHOTOS)

British actors Sienna Miller and Jude Law were engaged back in 2004, when Sienna was just 23 years old. But Jude, who has three children with ex-wife Sadie Frost, couldn't keep his hand out of the honey jar: He was caught cheating with the family nanny in 2005. The nanny promptly sold her juicy story to the tabloids, which was how Sienna found out about the affair. The wedding was called off, Sienna's mom called Jude "a bloody idiot" in The Daily Mail, and three years later, the ill-fated twosome gave it another try before splitting up again in February 2011.