Credit: Paul Morigi/

And baby makes five!

Cynthia Nixon's fiancee, Christine Marinoni, 43, gave birth to the couple's first child together Monday, her rep confirms to

The little guy -- named Max Ellington Nixon-Marinoni -- joins Nixon's daughter Samantha, 14, and son Charles, 8, from her previous relationship to photographer Danny Mozes.

The Sex and the City actress, 44, and Marinoni started dating in 2004 and announced their engagement in 2009.

And though they haven't tied the knot yet, Nixon has said they already feel like a family.

"Maybe I'm just lucky, but I feel like Christine is so amazing with our kids — because they’re our kids," she told The Advocate last year, adding that sometimes her children call Marinoni "Mommy."

"I feel like falling in love with her is part of being amazed at how she makes our family so much better."