Cooper announced the happy news on Instagram Tuesday.
"Scarlett and I are overjoyed to share that we welcomed Marigold Adele Hefner and Blossom Pearl Hefner into the world on Saturday, March 26th," Cooper wrote alongside a slideshow of sweet photos of Scarlett and their little ones. "Today, we are settling back in at home. How blessed we are to be gifted with their life. How lucky we are to be given this love."
The 31-year-old actress, who is best known for her role as Pansy Parkinson in the last three Harry Potter films, shared some of the same photos to her page, writing, "My heart grew twice as much this weekend as Cooper and I welcomed our daughters, Marigold Adele Hefner and Blossom Pearl Hefner into the world. Our home is full of love with our three daughters and we couldn’t be happier."
The couple are already parents to Betsy Rose Hefner, 1, whom they welcomed in August of 2020.
Their posts were met with plenty of congratulatory comments, with a few from Byrne's Harry Potter co-stars.
Afshan Azad-Kazi, who played Padma Patil in the film series, commented, "Love you so much! So proud of you 💕💕," while Ellie Darcey-Alden, who played a young Lily Potter in Harry Potter and the Deathly Hallows – Part 2, wrote, "So proud of you Scarlett! Those girls are so lucky to have you💗💗."
Cooper and Byrne announced they were expecting twins on Thanksgiving, with the U.S. Air Force Airman writing, "Scarlett and I will be welcoming two new members of the family this spring. We couldn’t be happier as we wait on the arrival of our twins. A very Happy Thanksgiving to all!"
Cooper and Byrne tied the knot in November 2019 in a courthouse ceremony.
Hugh Hefner's Son Cooper and 'Harry Potter' Actress Scarlett Byrne Expecting First Child Together