Burt Jenner, the eldest son of Caitlyn Jenner, is a new dad!

Burt and his longtime girlfriend, Valerie Pitalo, welcomed a baby boy on Thursday.

WATCH: Caitlyn Jenner Is Getting Another Grandchild

The 37-year-old race car driver announced the news with an adorable photo of Pitalo holding their newborn son against her chest while resting in a hospital bed.

"She did it!" Burt excitedly captioned the heartwarming snapshot.

PHOTOS: Stars Share Pics of Their Cute Kids

The happy couple first announced that they were expecting back in December, when Burt shared a picture of their baby's ultrasound.

"I promised to wait until we had the 'all healthy' update, and we got it yesterday," wrote Burt, who is Caitlyn’s son from her first marriage to Chrystie Scott. "My Lil boy, just chillin... So happy I can't see straight, he can't get here fast enough"

Congrats to the happy couple on the new addition to their family!

WATCH: Burt Jenner Says He and Caitlyn Are Closer Than Ever Since Transition

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