Robert Downey Jr. and Susan welcomed a baby girl, according to People.
The couple's newborn daughter joins the couple’s son, Exton Elias, 2, and the actor's 21-year-old son, Indio.
Details on the baby's name and birth have yet to be released.
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Last week at the BAFTA Awards, the "Avengers: Age of Ultron" star spoke about how fatherhood has changed his outlook.
"It's just the uncertainty of how nowadays you have all these things where you think you have much more of an understanding of what you’re going to get," Robert, 49, said. "And then this little soul lets herself be known to you, and it’s just like: You don’t know anything. It's great!"
The actor and his wife announced they were expecting a second child together on Twitter in July. He followed up the announcement with a Facebok post revealing they were expecting a girl.
WATCH: Robert Downey Jr. Talks Being A Dad Again; Helping His Troubled Son
"I don't know if it's a 'man's world,' but I'm certain women run it. Susan and I are therefore delighted to announce we are expecting a baby. Girl," he posted a few weeks later.
-- Jesse Spero
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