Penna Mae Ziering was born on April 25, exactly two years to the day after their first daughter, Mia Loren.
"We didn't plan it!" Ziering told the magazine. "Mia was born a week late and Penna was a week early."
Ziering, 49, says their daughter's first name in in honor of his late father, Paul, and Mae is the middle name of now four generations of women on Erin's side.
"Watching Mia & Pen in Erin's arms as they all sleep," Ziering tweeted on Friday. "Can't hold back the tears, wishing my parents were still around to bask in all this joy."
Ziering, who joins Chippendales in June, wed Ludwig in May 2010.