Olivia Namath, daughter of the football hall of famer, gave birth to a daughter, Natalia, May 21 in West Palm Beach, Fla, the Palm Beach Post reported Wednesday.
Namath, now living in Tequesta, Fla., said he was "very happy" with his new role.
"There are some things in life that are wonderful, and this is one of them," the 64-year-old Namath said. "I'm just happy that everyone's healthy."
He renovated a wing of his home for his daughter, 16, and granddaughter.
Olivia is Namath's youngest child with ex-wife, Tatiana. They have another daughter, Jessica, 21.