The couple welcomed their second child, on January 15, one month after they celebrated their daughter Harper's second birthday, confirmed E! News.
During the Toronto International Film Festival in September, Elizabeth announced her pregnancy on Instgram before hitting the red carpet with her husband.
The 34-year-old actress wrote, "Dressed and ready for the premiere of #Freefire. "And the premiere of baby Hammer Number 2!"
The duo managed to keep the baby's sex under wraps for quite some time until Hammer accidentally revealed it during an appearance on "Jimmy Kimmel Live!" while promoting his film "Birth of a Nation".