Sienna Miller has reportedly started a secret romance with another married actor.

The British star - recently split from long-time boyfriend Rhys Ifans - has allegedly caused oil-heir Balthazar Getty’s wife and four kids to flee their home after she discovered her husband’s relationship with her.

Getty - who stars in US sitcom Brothers And Sister - has apparently been enjoying secret dates with Miller around Hollywood after his clothes designer wife Rosetta fled to Italy.

A source tells the News Of The World, “Even though Balthazar loves his wife and children he cannot stay away from her. But Rosetta found out about them and has now fled to Italy.

"She can't believe her husband could do this to her. The whole family now know and everybody is devastated."