SIOUX FALLS, S.D. — A South Dakota high school teen is sharing an important night with his sister.

AJ Spader’s sister Rebekah was diagnosed with Myelodysplastic Syndrome, or MDS, several years ago. After a bone marrow transplant failed, the family decided to forgo any further treatment.

The Valentine’s Winter Formal at O’Gorman High School could have been AJ’s first dance with a date, but he tells KSFY that “Rebekah kind of trumped them all.”

Instead, AJ came up with the plan to make sure Rebekah got to experience this important rite of passage.

“He’s thinking about his sister and she’s not going to get to go to the prom or the formal when she’s in high school because she’s probably not going to make it to high school, so he just wanted to give her that memory,” said dad Tony Spader.

AJ made sure his sister got the whole formal experience, bringing her to dinner with his classmates and their dates.

“It’s fun to watch her live part of life where the disease doesn’t creep in, where she is just excited to be going and doing something that every child and every teenager gets to do.”

While the day may be all about his sister, it’s clear the evening is not just for Rebekah.

“I want to spend as much time with her as possible while she’s still doing good,” AJ said.

“A lot of times there’s a joy filled moment, but yet there’s a little sorrow because you know this is probably one of her last opportunities she’s going to have to do something like this,” Tony said.