Thomas Slater, 30, found out he had one of the rarest bone tumours in the world after breaking his leg playing rugby in 2004.
He started treatment at the Robert Jones and Agnes Hunt Orthopaedic Hospital in Shropshire.
However, he decided to postpone a major operation that was due to take place at the Orthopaedic Hospital when his brother Ian found out that he had acute lymphoblastic leukaemia.
Thomas waited until he could donate stem cells to his twin before having his own operation.
Now approaching their 31st birthdays at the end of September the brothers have decided to take on the three highest peaks in Britain in just 24 hours to raise funds for the Orthopaedic and Whiston Hospital, Liverpool.
The twins are taking on the challenge with dad Ian Slater, older brother Daniel and colleagues from their family business, Palletland, based in St Helens in Merseyside.
Ian said that he had made a full recovery since the devastating diagnoses when they were 15.
But he said Thomas is still undergoing treatment to help reduce the tumour and get some stability in his leg.
He now has a metal plate in his leg with 15 screws to strengthen the bone.
Ian said: “We wanted to be able to give something back to the hospitals that helped us, so we can improve the lives of others like us, who are going through hard and trying times.
"Any donation however large or small will mean a great deal to us and will be our motivation on the day.”
Anyone who wants to sponsor the twins can do so at gofundme.com/f/cea3sn-palletland-3-peak-challenge.