Egypt Dean, the couple's first child, was born Thursday night in New York. Beatz has two other children from previous relationships.
"I'm so thankful for everything I been blessed with in my life wowwwwww!" the rapper Beatz (real name: Kaseem Dean) tweeted late Thursday.
Keys, 29, and Beatz, 31, who have been together since 2008, got married over the summer.