Kennedy told RumorFix that she and Williams have named their newborn baby girl Samantha Rose Williams.
Samantha was born weeks ahead of her scheduled due date of April 23, her mother revealed.
Williams is also the father to 9-year-old Brandon Eric Williams, who is apparently very excited about his sister's arrival.
The actor has been married twice in the past, to Diane Martin from 1990 to 1992 and later to Ella May Matt from 1999 to 2006.
Williams is most famous for playing heartthrob Greg Brady on the popular 1970s sitcom The Brady Bunch.
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Watch a clip from The Brady Bunch below: