Blanchard's partner shared news of the baby's birth with a photo on Instagram.
The couple welcomed a son named Dakota Song Culkin, after the actor's late sister, Dakota, who died in 2008 at age 29.
Neither parent revealed the baby's name.
CONGRATS LEA! The former "Glee" star welcomed her first child, a baby boy, with her husband Zandy Reich, on Aug. 20.
Wyatt Morgan Cooper is named after Anderson's father who died when he was 10.
"I don't know anything about boys, so I'm so excited," Ashley Graham told Vogue during her pregnancy.
