Anna Kournikova, Enrique Iglesias Welcome Twins

Anna Kournikova and Enrique Iglesias are first-time parents - she gave birth to twins over the weekend ... TMZ has learned, but the real miracle is ... no one had a clue she was pregnant!

Sources in Miami tell us Anna had a boy and a girl Saturday in Miami, and their names are Nicholas and Lucy. The only thing overshadowing the blessed occasion is the fact they kept this whole thing a secret for 9 months.

Fact is Anna's been way out of the spotlight for more than a year now. The last photo we can find of the 36-year-old in public is this shot on a boat in Miami from November 2016.

They've been together since 2001, and although there have been marriage rumors for years - fueled by a HUGE rock on her hand - neither's ever confirmed it.