The former Cheers star took to Twitter on Tuesday (21Jun16) to announce the birth of grandson Waylon Tripp Parker, the new baby boy of her son William True Stevenson.

Kirstie posted a sweet black-and-white photo of William holding the newborn on his chest, and added the caption, "When your son has a son...bliss...yes this is my secret happy news as promised ...Welcome Waylon Tripp Parker."

The actress added another close-up shot of baby Waylon, who appears to be giving a smile to the camera.

"Just GOTTA send one more..proud Gammy (grandma)," Kirstie wrote.

William, 23, is Kirstie's adopted son with her ex-husband, actor Parker Stevenson. The former couple also adopted daughter Lillie, 22, in 1994.