Jack shares three daughters — Pearl Clementine, 11, Andy Rose, 8, and Minnie Theodora, 5 — with his ex-wife Lisa Stelly, while he and Gearhart are parents to Maple Artemis, 16 months.

"Happy Birthday to my wonderful son Jack," Pratt, 45, captioned a photo gallery of him spending time with his oldest child. "I thank God every day for you sweet boy.