Lively and Reynolds, who have been married since 2012, are parents to daughters James (5) and Inez (2).
The A-list duo recently welcomed a third daughter but have yet to unveil her moniker.
Reynolds shared a sneak glimpse of their new arrival back in October 2019 via Twitter with a touching photograph which shows the parents smiling alongside their newborn.
Lively recently spoke out about becoming of mother-of-three while promoting new film, The Rhythm Section.
During an appearance on Good Morning America, the 32-year-old admitted: "It's like going from two to 3,000."
"I mean, we have so many children. It's pretty crazy. We're outnumbered, and it's a lot."