It was back in September when John made the surprising announcement that he and Olivia were expecting, dropping the news during an interview on "Late Night With Seth Meyers."
The interview touched on the ups and downs of John's life over the last year, where he also shared that it was Seth and other close friends who staged an intervention and encouraged him to go back to rehab for several weeks.
Prior to Olivia, John had been married to Anna Marie Tendler from 2014 until they announced they'd split in May 2021, John filed for divorce in July. At the time, reports said Mulaney and Anna had broken up quite some time before the news was made public.
Little boy Mulaney is the first child for both Olivia and John.