Caitlyn Jenner Is Getting Another Grandchild - Find Out Who's Expecting!

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Caitlyn Jenner's family is getting bigger!

The 66-year-old former Olympian has another grandson on the way, after her son, Burt Jenner, 37, announced that he and his wife are expecting on Instagram Thursday, writing, "I promised to wait until we had the "all healthy" update , and we got it yesterday... My Lil boy, just chillin... So happy I can't see straight, he can't get here fast enough... Who wants to fab me a stroller with @kingshocks and @gladiatortires like you see at the 1000 every year?."

WATCH: Burt Jenner Opens Up About Caitlyn's Transition

In addition to Saint West earlier this month, Caitlyn received a grandchild from her son, Brandon Jenner, when Eva James was born in July.

In October, Burt revealed how he and Caitlyn have bonded "more now than ever" in the wake of her transition.

WATCH: Caitlyn Jenner Says Her 'Biggest' Holiday Tradition Is Kris' 'Over-the-Top' Christmas Eve Party

“There’s been some trade-offs, I’ll admit that,” Burt told Australia’s Today show. “But she is a better person. Honesty is always the building block for any relationship, and at least we have that now.”

Burt's baby announcement is obviously good news on this Christmas Eve, a day that Caitlyn is already so high on due to Kris Jenner's holiday soiree.

PHOTOS: Holidays 2015: Stars Get in the Spirit

Watch Caitlyn rave about her estranged wife's "over-the-top" Christmas get-together below.