Congratulations are in order for Chelsea Clinton and Marc Mezvinsky! The happy couple, who revealed they were expecting a second child in December, announced that they'd welcomed a son on Saturday via Twitter. "Marc and I are overwhelmed with gratitude and love as we celebrate the birth of our son, Aidan Clinton Mezvinsky," Chelsea, 36, shared with her followers. Aidan joins big sister Charlotte, 1, and his grandparents, former President Bill Clinton and Democratic presidential candidate Hillary Clinton, couldn't be more thrilled.

"We are overjoyed to be grandparents again with the arrival of our grandson, Aidan Clinton Mezvinsky, born on Saturday, June 18, 2016," Bill and Hillary said in a joint statement. "We are all over the moon as Chelsea and Marc welcome Charlotte's little brother to the world and grateful for our many blessings. Chelsea and Aidan are both doing well and enjoying this very special time together."

On Sunday, Chelsea took to Twitter to share a first look at her little bundle of joy, writing, "At 7:41 AM Saturday, our family and hearts expanded with Aidan's arrival. We are blessed."