Brennan Simkins was diagnosed with a rare form of leukemia at the age of seven. At one point, he was given less than a one percent chance of survival.

But Brennan overcame the odds and beat the disease. Now, his father has written an inspiring new book, "Possibilities," which tells the story of how Brennan's fighting spirit changed the lives of others and laid the foundation for new, proven therapies and trials in the fight against pediatric cancer.

Father and author Turner Simkins revealed on "Fox and Friends Weekend" this morning that Brennan is doing well and is in his fourth remission.

"Long story short, he had four bone marrow transplants in 18 months, which was unprecedented," Simkins said. "After the first relapse, we were really given no other choices but comfort care. So it was quite a journey."

He explained that St. Jude Children's Research Hospital was the only hospital willing to give further treatments a shot.

Simkins said that "Possibilities" isn't just Brennan's story. It's also a tribute to all the brave kids and families they met at St. Jude.

Watch more in the clip above, including a surprise phone call from country music star Darius Rucker!

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