When Reuben Byrne died in his sleep just five days before Christmas his big brother Harry climbed into the bed and sang to him, tenderly stroking his head.

Then he told his mum he was going to climb a mountain in the little boy's memory.

And next month the eight-year-old, who hit the headlines last year when he raised almost £40,000 for charity with Reuben by his side, is planning to deliver on that promise by tackling the three Yorkshire Peaks.

Harry and his family always knew that life would be short for Reuben, who was born with a condition so rare that there are only 20 cases recorded worldwide.

There's no name for it yet, but it causes brain deterioration and seizures. It is the same condition that claimed the life of the children's older sister Olivia, who died nine years ago aged eight months. Reuben was 27 months old.

Along with his mum Sophie, dad Sean and baby brother Felix, Harry, from Larkhill, will scale more than 7,000ft over three days from 11 April. The inspiring family hope to raise funds and awareness for Julia’s House children’s hospice in Wiltshire and Naomi House & Jacksplace in Hampshire, plus four other charities who have been there when they needed them most.

Sophie said, “We’d had a lovely last evening together. Reuben had been looking at all the Christmas lights, and Harry and I shared cuddles with him on the sofa while we watched a film together.

“The next morning, Sean went in to check on Reuben and he had passed away. Even though we knew his condition was bad, it shocked us all because he had been doing so well.

“After we told Harry, he came into Reuben’s room and immediately climbed into bed with his little brother and started singing to him and stroking his head. I was there looking at my boys, my heart was breaking for them. Tears were running down my face and I had to bite my tongue to stop myself from wailing and ruining that moment," she said.

“After about 10 minutes, Harry came off the bed, looked out of the window and said, ‘I’m going to climb a mountain for Reuben. He knows that Sean and I climbed the three national peaks in his sister Olivia’s memory, and he really wanted to do something positive like that for Reu Reu too.”

“We’ve had extremely tough days following Reuben’s passing and Harry has astonished us with his strength. When we said our last good byes, Harry drew a picture of Reuben smiling, and told us: ‘We’re sad but Reuben is happy because he’s free.’

She said: “Harry wasn’t just Reuben’s brother, he was also a fantastic young carer. When Reuben had a seizure, he would hold his oxygen and tell him: ‘It’s okay Reu Reu.’ It all came so naturally to him and Reuben was always so happy in the arms of his big brother.”

Last year, with the help of his friends and the community, the St Michael’s Primary School pupil completed a Race Around the Moon distance challenge and a Hospice to Hospice. hike. His marathon efforts earned the attention of national media and an appearance on the Russell Howard Hour.

By taking on the three peaks of Pen-y-ghent at 2,227 ft, Whernside at 2415 ft and Ingleborough at 2,372ft, Harry and his family hope to raise £5,000 for the charities that continue to support them - Julia’s House children’s hospice, Naomi House & Jacksplace, Ronald McDonald’s House, Saffa, Sandcastle Trust and Royal Artillery Charitable Fund.

Sophie said, “Reuben fought through challenge after challenge and he always managed to smile. That rubs off on you, how resilient he was. I feel like all the miles we walked and taking on this new three peaks challenge is nothing in comparison to what Reuben went through.”

"He taught us all to live in the moment and enjoy the simple things in life. Just holding his hand would make him happy. He didn’t need much – just love and care. I think there’s a lot we can all learn from that.”

Julia’s House sibling worker, Tracey Griffin, continues to visit Harry at home regularly. She said: “Harry is an incredibly caring young person and you can’t fail to be inspired by his energy and compassion for other people. We’re so very thankful to Harry and his wonderful family for once again fundraising for the seriously ill children and families that we care for, and we wish them all the best in their special three peaks challenge in memory of Reuben.”

Peter Abrahams, head of supporter services, Naomi House & Jacksplace, added: “Harry is an inspiration to me, and to all of us and Naomi House & Jacksplace. His determination, courage and commitment motivated people from across the UK to get involved and support him in his recent challenge to Race Around the Moon.

"The money Harry raises helps to make a real difference to the families who use our services. Our hospices support life limited and life threatened children and young adults, as well as their families. Once again, Harry has set the bar high with an amazing fundraising adventure! Harry, we’ll be cheering you along on every step of the way!”

To sponsor Harry visit justgiving.com/team/Mountaintrekkes