The former first daughter, 38, is expecting her third child with husbandMarc Mezvinsky, she announced on Tuesday.

“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 wrote on Twitter.

The third-time mom-to-be added, “We cannot wait to meet our newest addition later this summer.”

Clinton and Mezvinsky, a hedge fund executive, married in 2010.

Back in 2015, shortly after giving birth to Charlotte, Clinton told PEOPLE that being a mom changed her world.

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“I didn’t know I could care more intensely about anything until I became a mom,” she explained. “Somehow I love my husband even more, I love my parents even more. I feel even greater urgency about the work that I do, particularly around women and girls being a mom of a daughter.”

“And I think my love for Charlotte has just opened more space in my heart and my brain that I didn’t even know was there.”

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Chelsea Clinton

Motherhood also inspired Clinton to become a children’s author. She’s penned four books so far, includingStart Now!: You Can Make a Difference—released in October.

“I found books really empowering as a kid and hope that this book helps empower kids today,” Clinton told PEOPLE. “[My kids] love being read to and talking about what they’re reading in books. Particularly for young readers, books are not only a way to help break down and communicate ideas [but] stories of real empowerment.”

Start Now!gives young readers a better understanding of big issues like hunger, health, bullying, climate change and endangered species. Written for kids 7 to 10 years old, the book also shares tipsand true stories about activismto inspire readers to make their own impact.

Source: Chelsea Clinton/Twitter

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Chelsea Clinton and daughter Charlotte

And while Charlotte and Aidan won’t be able to read her new book for a few years, that hasn’t stopped Clinton from teaching her kids about the issues she cares about.

“My children are still relatively small. They’re 2 and 4. My daughter turned 4 last week and yet they are people,” the Vice Chair of theClinton Foundationsaid. “So we talk to them and engage them in issues and in ways that help make the world the way we want it to be. We talk about climate change and using energy responsibly.”

Clinton continued, “We do it at home with our climate-smart light bulbs, or making sure we turn off water when we’re not using it so we’re conserving water. Our kids help us carry out the recycling.”

source: people.com