The proud dad shared the news via Instagram, posting a picture of a flower arrangement with the words "It's a Girl."
"Words cannot express the joy my children bring me. We are very excited to welcome the newest member of our family.. I love you with all my heart. @crownv_16 #thefedz #sixthman I mean #sixthwoman," Federline captioned the pic.
The new baby is Federline's second child with Prince -- the couple already has 2-year-old daughter Jordan -- and sixth overall. The former backup dancer also has two kids, Sean, 8, and Jayden, 7 with ex wife Britney Spears and two more with ex girlfriend Shar Jackson, Kori, 11, and Kaleb, 9.
The new parents married in August of 2013 at an intimate ceremony in Las Vegas.
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