Us broke news in October 2012 that the British director, 45, and model Ainsley, 32, got engaged after several years of dating. Their newborn now joins big sister Rivka, 18 months, and brother Rafael, 2.
Ritchie also shares sons Rocco, 13, and David, 8, with ex-wife Madonna, 55. The couple split in 2008 after eight years of marriage. Despite their bitter divorce, they reunited last July to celebrate Rocco's bar mitzvah at the Kabbalah Centre in New York City.
"I enjoyed my first marriage. It's definitely not something I regret. The experience was ultimately very positive," Ritchie said of his marriage to the pop superstar in Details magazine in 2011. "I love the kids that came out of it, and I could see no other route to take."