Sister of 12-year-old cancer patient donates bone marrow for potentially life-saving transplant

What could be a life-saving bone marrow transplant for 12-year-old cancer patient Colton King is now complete. It's all thanks to his 17-year-old sister Kaylee King and her bone marrow, which doctors have said is the perfect match.

"It means a lot to me. I know I probably can't grasp how big and important this is now, but the significance of being able to save my brother's life is not something I'll probably be able to do ever again," Kaylee said.

Back on January 4, Kaylee did her part and was placed under anesthesia for about three hours as doctors used needles to extract her bone marrow to put into Colton's body. The next day it was Colton's turn. As his mom Stacy King explained his procedure was similar to that of a blood transfusion and took about four hours to complete.

RELATED: Fish Hawk boy with rare form of leukemia cleared for life-saving transplant after sister was found to be match

"They were monitoring things really closely and what's amazing to me is that the human body knows where things go," Stacy said. "Her marrow went right to where the marrow is supposed to be within a few hours, which I think it's really incredible."

Just six months ago, Colton was perfectly healthy playing baseball when his mom noticed he was resting and tired more often than normal. He was eventually diagnosed with a form of leukemia so rare his pediatric oncologist has only seen one other case in his 20 years of practice.

With the transplant now complete, doctors will now wait to see how Colton's body reacts.

MORE: Boy with rare form of leukemia to receive life-saving bone marrow transplant from sister

"We were so incredibly relieved. When Kaylee and her dad were driving here, I was just praying, God, keep them safe, get them here safely because at that point Colton's immune system had been wiped out, and he needed Kaylee's," Stacy said.

Because of chemo and radiation, Colton is now without an immune system, which is why he and his mom have been confined to AdventHealth for Children in Orlando for the next few weeks. Eventually, once Colton is healthy enough he and his family will move to the Ronald McDonald House near the hospital.

They're hoping he'll be back home and healthy in Tampa by March or April.