Sienna Miller having affair with multi-millionaire oil heir Balthazar Getty?

Matthew —who stars with Getty in the hit sitcom Brothers And Sisters—introduced the millionaire actor to Sienna last summer.

Miller has been enjoying romantic nights with the tycoon actor and dad-of-four Balthazar Getty for perhaps up to 3 months. Lately the enamored couple have been holed up together day and night in Hollywood. Despite playing a cat and mouse game to stay out of the headlines they have been spotted secretly meeting at restaurants near their hillside hideaway.

A source revealed: “They went to great pains to find a place where they thought nobody would find them. They daren’t go out together, so they spend most of their time inside. When they do leave, they go separately.”

In one rendezvous on Thursday, 26-year-old Sienna drove to a restaurant while former heroin addict Getty, 33, even bicycled there to try to avoid being spotted with her.

Inspite of the cloak and dagger sneaking around, Getty’s heartbroken wife found out about the affair. Getty’s clothes designer wife Rosetta Millington whom he wed in 2000, reportedly has abandoned their Hollywood hilltop mansion to RUN AWAY to Italy with their four children —the youngest born only eight months ago—after having it out with her wandering husband.

Apparently Getty tried to cover up a visit last month to see Sienna in Prague—where she is filming her new movie GI Joe—by saying he was visiting his “sick mother” in Germany.

Two weeks ago Rosetta, 32, found out!

(source)