First child for Sienna Miller and her boyfriend Tom Sturridge.

"G.I. Joe: The Rise of Cobra" and "Interview" actress Sienna Miller and her boyfriend "Pirate Radio" actor Tom Sturridge are expecting their first baby togethera source confirms to Us Weekly. The 30-year-old actress and Sturridge, 26, have been together for a year and "don't have plans right away to marry, if at all," the source says.

According to Us Weekly magazine, the couple announced the pregnancy to friends in London over the holidays and those they told were "not surprised by the news." "Friends are really happy with her relationship with Tom," a source tells Us. "He's younger, yes, but he's mature and he's a good guy."

"They just spent the holidays in Paris together after they announced the news in London," says the source. Miller's rep could not be reached for comment. A rep for Sturridge tells Us: "We don't comment on our client's personal lives at all."

In September, the duo went on a double date with Sturridge's pal Robert Pattinson and girlfriend Kristen Stewart. The foursome knocked back drinks at London's Groucho Club. "They looked happy," a witness told Us. In filming "G.I. Joe: The Rise of Cobra" and "Alfie," she met her on-and-off boyfriend "Sherlock Holmes" actor Jude Law. Last February, the pair split up for the second time.