Jenna Bush Hager Says Watching Sister Barbara's 'Dreams Come True' as a Mom Is an 'Incredible Gift'

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Jenna Bush Hager is loving life as an aunt.

While chatting with PEOPLE about her new partnership with Dawn, for which she wrote a digital children's book entitled The Wonderful World of Blue, the Today co-host opened up about watching her twin sister Barbara Bush Pierce recently become a mom as well as the sweet bond between her three children and their 1-year-old cousin Cora Georgia.

"I think watching somebody you love become a mom, watching [Barbara] have her dreams come true has been this incredible gift," Bush Hager tells PEOPLE.

"She loves being a mom — it's just the most natural, wonderful thing for her," she adds. "I've loved it. I love being an aunt. I love that little baby pumpkin!"

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Bush Hager says the love between all the cousins — she and husband Henry Hager share Henry "Hal" Harold, 2, Poppy Louise, 6, and Margaret "Mila" Laura, 9, while Bush Pierce shares Cora with screenwriter husband Craig Coyne — has been fun to watch grow, particularly with her youngest child.

"Hal names every baby doll in the house baby Cora Georgia and it's so cute," she says with a laugh. "He didn't have a baby — his baby is his little cousin. It's the most fun to witness."

She adds of the family's recent first birthday party for Cora, "We just got to celebrate her and it's so fun because they're so close in age."

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Bush Hager says her children played a huge part in her decision to partner with Dawn on their new initiative and continuous work with wildlife as she encourages her kids to advocate for good causes.

"I know the work Dawn does on behalf of wildlife and I know how it's more important than ever," she tells PEOPLE. "As a mom of three kids, I wanted a way for our kids to be wildlife heroes and get involved."

"I feel like children's books are a perfect way to introduce kids to concepts they may not be aware of and make sure they know they can do good," the children's book author continues. "Our kids are capable of whatever we expect of them, so if we expect them to help us save the world, they're going to save the world."

Says Bush Hager, "The Wonderful World of Blue is such a great opportunity because it gives specific details on how our kids can help and I think that is what kids want — they want to be thought of as the empowered, awesome creatures that they are. They're good forces in this world."