'Dream Baby' Made Possible After a Sister Gave Her Twin with Cancer the 'Beautiful' Gift of Surrogacy

Cathey Stoner has more than earned the title of "Best Aunt" after giving birth to her new nephew, John Ryder Sharp.

What had started as a quick joke between twin siblings became reality when Stoner's sister, Sarah Sharp, 33, was diagnosed with choriocarcinoma, a rare and aggressive form of cancer in the uterus, they tell PEOPLE. Doctors first found it in 2018, nine months after Sharp gave birth to her first child, daughter Charlotte, now 4, after she began experiencing severe uterine bleeding. Doctors told Sharp she may need a hysterectomy, and Stoner told her: "If they take your uterus, I'll have your babies!"

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Initially, Sharp was able to keep her uterus, but a week later a tissue sample showed that she had cancer. She started on intensive chemotherapy with Stoner, a mom to Ruth, 7, and Samson, 4, by her side. But after six months of treatment, it was clear that Sharp needed a partial hysterectomy and would be unable to carry another child.

"I was broken," Sharp says of the news. "My husband [Richard] and I had to grieve what we thought life would look like."

By that point, Stoner and her husband Alex had seriously discussed making what had been a joke a true promise.

"We walked with Sarah and Richard through some dark days," Stoner says. "We didn't know if she was going to live at one point. We wanted to give them this hopeful thing. We felt called."

When Stoner told Sharp that "if you want to grow your family, I would love to do that," Sharp says that it was "the biggest act of love I've ever received — pure, unconditional love."

Sharp still has her ovaries and was able to undergo an egg retrieval to produce three viable embryos with her husband, one of which was transferred into Stoner in December. The sisters live just 25 minutes apart — Stoner in their hometown of Franklin, Tennessee and Sharp in Nashville, and it was easy for them to take care of each other. Sharp would bring her sister homemade lemon cream pies, give her foot rubs, and in April both couples went on a "babymoon" to Cancun.

For more on the twin sisters and their path to surrogacy, pick up a copy of PEOPLE, on newsstands Friday

Stoner did wonder what her kids would think of her growing stomach that would soon produce their cousin, not a sibling.

"I wanted to make sure it wasn't confusing," she says. "We told them we were taking care of their cousin, loving on him and babysitting him until he could go home, and they got it. My hope is that they look back on this and learn and know the foundation of our family, which is service and loving each other and sacrifice."

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And Stoner says that she didn't have too much trouble with the idea that she wasn't carrying her own child.

"I knew it was Sarah's baby. I've connected with him, but I've felt mentally ready to pass him on to her," she says. "I've had such peace about the whole thing from start to finish."

On Aug. 18, Stoner delivered John Ryder Sharp with her sister, husband and brother-in-law by her side.

"It was a whirlwind of emotions," says Sharp. "He came from my sister, but I could tell he was mine."

Stoner had wondered if she would feel an urge to reach for him, "but I didn't," she says. "I felt very proud of him, but he feels like theirs. He definitely looks like them."

After the umbilical cord was cut, Sharp held him against her skin and whispered to her son, "I love you. We've prayed for you. We're so happy you're here," before telling her sister, "Thank you, thank you, thank you."

John Ryder is healthy and happy at home with the Sharps. Stoner and her family visit frequently, as she's pumping breast milk for her nephew, and the twin sisters are busy telling their story on their podcast Talk to Me Sister and working on a book about the experience. Sharp is also thinking about the potential of her other two embryos, but for now she's just enjoying her new "dream baby."

"I haven't had much sleep because I just watch him; I still cry when I look at his face," she says. "When something terrible happens, it can feel like that's the end. But life can surprise you. John Ryder is such a representation of hope and that life can be better again."

• With reporting by MORGAN SMITH