Getty Images Sienna Miller is a mom of three! The 44-year-old actress confirmed that she and partner Oli Green, 29, have welcomed their third child. How did Sienna Miller confirm the happy news? "It's happened," she told E! News on Monday (May 11). "I have a tiny baby next door." She spoke about going from having two children to three: "It feels like stringing sentences together is a bit challenging. I'm on very little sleep, but I'm madly in love with my baby.