By Paul Burton

BOSTON (CBS) – The bond between six-year-old Logan and his baby sister three-year-old Giana is inseparable.

If she’s not eating his food, he’s chasing her around and the two are never more than an arms-length away.

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“She’s our miracle baby. She’s been fighting since day one for life. I feel like they have this bond that we didn’t see prior to transplant,” their mother, Marissa Lesselroth said.

Logan and Gia (WBZ-TV)

Logan and Gia (WBZ-TV)

At four and a half months old Gia was diagnosed with an aggressive form infantile leukemia. She beat it the first time but then relapsed last May, so this Florida family moved up to north to get their treatment at Dana-Farber/Boston Children’s Cancer and Blood Disorders Center.

“Because of Gia’s type of leukemia and because of the length of her disease it was felt that transplant was the best of long term care,” said Dr. Steven Margossian an oncologist with Dana-Farber/Boston Children’s.

It turns out her big brother Logan was more than just her best friend but a perfect match for a bone marrow transplant. “She means a lot to me. I Gave Gia my bone marrow,” Logan said.

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Logan and Gia (WBZ-TV)

Logan and Gia (WBZ-TV)

Logan says the pain of the procedure was not easy for either of them. “I was scared for the surgery then I came over it,” Logan said.

Logan was even brave enough to push the start button on the machine. While in the hospital Logan wrote a book about the whole experience. He calls it “Logan The Brave Bone Marrow Donor.”

Logan says he wrote his book and drew all the pictures so others kids who have to go through the same frightening experience can also be brave.

“I wrote this book to not make other families scared for their kids,” Logan said.

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Mom is so thankful that both of her kids are doing well today. “I am so proud of him. He’s my hero and Gia’s hero. It’s pretty special,” Marissa said.

Paul Burton