Chelsea Clinton announced today that she gave birth to a son, Aidan Clinton Mezvinsky.

The former (and possibly future) first daughter posted the news on Twitter late Saturday morning.

Clinton and husband, Marc Mezvinsky, also have a daughter, Charlotte, who’ll be 2 in September. She and Mezvinsky, an investment banker, married in 2010. They first met as teens and attended Stanford University together.

Clinton, 36, has been an active presence on the campaign trail for her mother, presumptive Democratic presidential nominee Hillary Clinton.

Hillary Clinton speaks frequently and passionately about her role as a grandmother. “There’s just nothing better,” she said in an interview with People Magazine. “I’m experiencing sort of what my mother experienced with Chelsea, because you’re so focused on just enjoying and marveling and loving to the Nth degree but you also have this perspective like, ‘Oh my gosh, I want to make sure that the world is okay and that, you know, things are right, and we have to save the planet.’ “