Welcome to Parenthood, Steve Martin.
At 67, the comedy great and his 41-year-old wife Anne Stringfield "had a baby" in December, "and how they kept it a secret nobody knows," an insider told the NY Post.
"Steve's very private," the source told the paper. "They are thrilled. They worked hard to have the baby."
The Cheaper By The Dozen star and Stringfield, a journalist for The New Yorker magazine, were seen recently with a baby in Los Angeles. They have been married since 2007; Steve was previously married to actress Victoria Tennant from 1986 until 1994.
Martin had not commented about the reports on his Twitter page as of early Thursday.