(CNN)Chelsea Clinton is out with the first photos of her new son, Aidan Clinton Mezvinsky.
"At 7:41 AM Saturday, our family and hearts expanded with Aidan's arrival. We are blessed," Chelsea Clinton tweeted late Sunday afternoon.
Her parents, former President Bill Clinton and 2016 presumptive Democratic presidential nominee Hillary Clinton, quickly followed with their own messages about the second child for Chelsea Clinton and her husband, Marc Mezvinsky. Aidan's sister, Charlotte Clinton Mezvinsky, was born in September 2014.
"What a joy being with our new grandson, Aidan. So grateful. -H," wrote Hillary Clinton, with "-H" a sign that the tweet was directly from her, not a staffer.
"Aidan has made two dads very happy this Father's Day. Hillary and I are thrilled for Marc and Chelsea!" Bill Clinton tweeted at about the same time.
The Father's Day messages followed Chelsea Clinton's announcement about the family addition a day earlier, over her Twitter and Facebook accounts.
"Marc and I are overwhelmed with gratitude and love as we celebrate the birth of our son, Aidan Clinton Mezvinsky," the former first daughter tweeted on Saturday.
Hillary Clinton regularly mentions her granddaughter, Charlotte, at political events and is often asked about the baby when she works the rope line after events, with people asking for updates on Charlotte's progress with walking and talking.
Charlotte, though, has not made an appearance on the campaign trail, in part because Clinton wants to give the child some semblance of privacy.
"Until it happened to me, I just could not understand the impact," Clinton said this month about being a grandparent. "It is truly like falling in love all over again. There is nothing like it."
She added, "It's transformational and until you did it, it is hard to know. And it has for me been an absolutely life-changing experience."
Chelsea Clinton married Mezvinsky, the son of two former members of Congress, in 2010. Ever since their daughter's nuptials, Bill and Hillary Clinton have applied good-natured public pressure on her to make them grandparents.
In April 2012, Hillary Clinton told ABC it wasn't "really up to" her whether she would ever earn the grandma title, but added, "I would like to have that title. ... I think I'd be pretty good."
Chelsea Clinton has regularly said that her parents were "unapologetic" in their pleas for grandchildren. "(They) are not shy about saying that in public and private," she told ET in 2013.
On Saturday, Bill and Hillary Clinton issued an effusive statement about Aidan.
"We are overjoyed to be grandparents again with the arrival of our grandson, Aidan Clinton Mezvinsky, born on Saturday, June 18, 2016," the couple said.
"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."