“He was our little superhero and put the biggest fight up but he was needed else where.
“There are no words to describe how heart broken we are.
“Thank you everyone for all your support and kind words. Sleep tight baby boy and fly high with them angel.”
Bradley’s family also had close links with Everton after the club pledged £200,000 towards his treatment when he was mascot for the match between Sunderland and the Toffees.
He went on to be a mascot for the Merseyside club too.
Chairman Bill Kenwright said: ”One of football’s all-time greats. We are so privileged to have known him…and will always be proud that he chose us as his second club.
Sunderland described him as “an inspiration”.
The club said they extended their love to his parents Gemma and Carl and his brother Kieran.
A statement said: “Bradley captured the hearts and minds of everyone at our club with his indomitable spirit, tremendous courage and beautiful smile, which could light up even the darkest of rooms.
“He was truly an inspiration. His heart-warming friendship with players and staff alike epitomised the impact this wonderful little boy had on everyone he met.
“He had a special relationship with Jermain Defoe and their feelings for each other were evident for all to see.
“Jermain, naturally, is heartbroken. Bradley’s story not only touched our club and our fans, but also the wider football community.
Defoe broke down in tears on Thursday at a press conference with his new club, Bournemouth, when he was asked about their special bond.
The Premier League star said: “There is not a day that goes past where I do not wake up in the morning and check my phone or think about little Bradley because his love is genuine and I can see it in his eyes.
“It is special.”