Brothers Harry, 10, and Max, 13, from Leeds, will compete in the athletics.
Harry was just one when he had a liver transplant, and his brother Max, was 11 when he also needed the same surgery as a result of a rare genetic condition.
Their mother Laura said the Games played “a massive part” in her children’s recovery.
“To be able to go and partake in something and watch them doing something together is kind of like a release, it’s like the end of all the really difficult times and it’s just nice to do something positive and normal without these shadows.”
For many participants, the Games are also about encouraging people to have conversations about their final wishes.
More than 8,000 people are waiting for a donor, according to NHS Blood and Transplant.
Mahmud Nawaz lost his wife in 2004 after she suffered a brain haemorrhage. She was just 32 but had registered as a donor and her organs saved four lives.
“I think there’s some real power in the Games in creating that conversation, creating that awareness and creating that joy of all the communities coming together. And if we can inspire through our leaders, through our media, through the Games, people to have that conversation, tell their loved ones what they want to do, that will help us save lives,” he said.
Since his wife’s death Mahmud has been keen to encourage people to tell their loved ones about organ donation, to carry a donor card and to register their decision on the organ donor register.
“In South Yorkshire, we’re behind the curve – 36% of us are on the organ donor register. The national average is 40% so we need to drive more conversations.”
The opening ceremony will start at 18:15 BST on Thursday with a parade from Tudor Square and a flame-lighting ceremony inside Sheffield City Hall.
