Over the weekend Hillary Clinton became a grandmother for the second time.

Chelsea Clinton, 36, announced her pregnancy in December. Clinton told PEOPLE magazine that he or she will be very lucky to have 20-month-old Charlotte as a big sister.

On Saturday, Clinton posted to Twitter: “Marc and I are overwhelmed with gratitude and love as we celebrate the birth of our son, Aidan Clinton Mezvinsky.”

Marc and I are overwhelmed with gratitude and love as we celebrate the birth of our son, Aidan Clinton Mezvinsky.

— Chelsea Clinton (@ChelseaClinton) June 18, 2016

Only hours ago, she published the first picture of her newborn son, captioning the image “At 7:41 AM Saturday, our family and hearts expanded with Aidan’s arrival. We are blessed.”

At 7:41 AM Saturday, our family and hearts expanded with Aidan’s arrival. We are blessed. pic.twitter.com/QKUMV3ls4N — Chelsea Clinton (@ChelseaClinton) June 19, 2016

Clinton married hedge fund manager, Marc Mezvinsky, in 2010.

Hillary could not contain her excitement over the birth of her second grandchild, posting a beautiful picture to Instagram of her and Bill nursing baby Aidan.

What a joy being with our new grandson, Aidan. So grateful. -H A photo posted by Hillary Clinton (@hillaryclinton) on Jun 19, 2016 at 1:38pm PDT

When interviewed by PEOPLE magazine in February, Hillary said: “I think this baby is going to be so lucky to have these two incredible people as his or her parents. That’s what I’m waiting to see.”

In a press statement, the presumptive Democratic nominee and the former President expressed that they were “over the moon” and “grateful for our many blessings”. They concluded that they were absolutely “overjoyed to be grandparents again”.

Statement from Bill and Hillary Clinton, who say the family is “over the moon” to add a newborn pic.twitter.com/uxzP1ZbcbJ — Jennifer Epstein (@jeneps) June 18, 2016

Baby Aidan came just in time for Father’s Day in the US, much to the joy of 69-year-old Bill.

Aidan has made two dads very happy this Father’s Day. Hillary and I are thrilled for Marc and Chelsea! pic.twitter.com/vPuwDA3Lvr

— Bill Clinton (@billclinton) June 19, 2016

In the past, Hillary has said that being a grandmother is one of her proudest achievements.

Watch Hillary Clinton discuss being a feminist with Lena Dunham.