Ollie Higgins from Magherafelt passed away on Saturday at the Royal Victoria Hospital for Sick Children.
It is understood that the youngster, who only turned four on May 30, had been ill for several months.
Ollie’s untimely passing is being mourned by his heartbroken parents James and Chantel, big sister Lucy, grandparents Oliver and Mandy (Higgins) and Richard and Sandra (Randlesome), aunts Rebecca and Corrina and the wider family circle.
Writing on social media, Ollie’s father James announced his passing on Saturday afternoon.
He wrote: “My son lost his fight today at 1.11 pm. He did me proud and made me the proudest father a man could wish for.
“He went peacefully and is no longer in pain. He earned that much and is forever a hero in my heart. Rip my little son, my little Hulk.”
In a statement, Castledawson-based construction manufacturer and supplier, Essential Design Group, which is run by his grandparents, Oliver and Mandy, said: “Ollie was a little warrior and he fought hard to the end.
“Ollie had an amazing personality and he touched everyone’s hearts that knew him.
“Ollie will be sorely missed. May he rest in peace. Heaven has gained another Angel.”
Angel Wishes, a group set up to support children throughout Northern Ireland fighting cancer, said it was devastated by the news of Ollie’s passing.
“It is with a very heavy heart we inform our Angel Wishes families of the passing of our wonderful little Ollie,” they said.
“I know many of you will have got to know Ollie and his devoted parents James, Chantel and sister Lucy throughout your time in hospital and like ourselves will be devastated by this news.
“James and Chantel will want you to continue to stay strong for your child as they did for Ollie.
“Our thoughts and prayers go to Ollie’s entire family at this very sad time.
“Fly high wee Ollie.”
Ollie’s funeral service will take place at St Swithin’s Parish Church, Magherafelt at 2.15 pm today.
He will be laid to rest in Polepatrick Cemetery, Magherafelt.
His family have requested that donations in lieu of flowers be made to Angel Wishes, payable to Garvin’s Funeral Service, 15 Ballyronan Road, Magherafelt.