Clinton and Mezvinsky revealed back in January that they were expecting their third child.
"Marc and I have loved watching Charlotte be such a wonderful big sister and we're excited to watch Aidan become a big brother!" Clinton tweeted at the time. "We cannot wait to meet our newest addition later this summer."
Earlier this year, Clinton expressed how being a mom inspired her to become a children's book author.
"[My kids] love being read to and talking about what they're reading in books," she told People in October. "Particularly for young readers, books are not only a way to help break down and communicate ideas [but] stories of real empowerment."
Check out the Clinton family tweets below.
This morning we welcomed our son, Jasper Clinton Mezvinsky. We are overflowing with love and gratitude and can't wait to introduce him to his big sister and brother.