Savannah Miller Tweets her love for Sienna's baby Marlowe
The fashion designer has put an end to the speculation surrounding Sienna's newborn's moniker.
Savannah Tweeted today about her niece: "Marlowe I love you....."
Sienna's first child was born last weekend, but no further details have been released by the model and partner Tom Sturridge, 26.
News of her pregnancy first surfaced in January but tight-lipped Sienna didn't confirm the news until April.
The 30-year-old told UK Vogue: "I'm feeling fine. It's all progressing nicely and it's very exciting."
Welcome to the world, Marlowe!