"Welcome Rio! Our first baby girl to join our family!" she tweeted on Thursday, July 18. "@theoliverhudson and Erinn, thank you for bringing so much JOY to our lives! #happiness."
Rio is Hudson and Bartlett's third child together and only daughter. Married since 2006, the couple are also parents to two sons, Wilder, 5, and Bodhi, 3.
Hudson, 36, is Hawn's oldest child with second husband Bill Hudson, whom she divorced in 1980. The exes also had a daughter, Kate Hudson, 34, who now has two kids of her own. Since 1983, Hawn has been in a relationship with Kurt Russell, with whom she has a son, Wyatt.