Sienna Miller Welcomes Daughter Marlowe

Sienna Miller has a new fan.

The actress, 30, welcomed a daughter with boyfriend (and rumored fiancé) Tom Sturridge, 26, over the weekend in London, a source confirms to PEOPLE.

“Marlowe I love you,” Miller’s sister Savannah Tweeted Tuesday, reportedly revealing the moniker for the new addition.

So what’s in a name? Of the Old English origin, it means “driftwood,” defined as pieces of wood that float in the water or are washed ashore.

The couple, who were first spotted together last spring, remained mostly mum after news broke of Miller’s pregnancy in January, except for a brief comment to Vogue U.K. in April.

“I’m feeling fine,” she revealed. “It’s all progressing nicely, and it’s very exciting.”

And the new parents seemed to be quite prepared for their little addition: Months after debuting her baby bump in February, Miller was photographed leaving her London baby shower in May.

— Alison Schwartz