His girlfriend might have a young son, but Jim Carrey, 47, is now a proud grandpa!

Early Friday morning, Carrey’s daughter, Jane, 22, gave birth to her first child, a boy, named Jackson Riley Santana, weighing 7 pounds and 11 ounces.

Jane is a singer-songwriter for the alt-rock The Jane Carrey Band and the father is Alex Santana, the lead singer of the metal band Blood Money. The two were married in November.

Jim twittered a photo of his new grandson. “Jackson Riley Santana, My Grandson, Born today! This is what 7lbs.11oz. of Calfornia dynomite looks like!” he wrote.