Doctors believed J’ssiah Brown’s life had been saved when his brother Kyerell, seven, donated his bone marrow so they could once again play together.
But their mother Jeanene Walters, 28, was handed a devastating blow when they learnt the leukaemia is back and British doctors say they can do nothing for it.
The family, of Camberwell, south east London, is now trying to raise #150,000 to get J’ssiah state-of-the-art proton beam treatment in the USA, or Israel.
The treatment, that the parents of five-year-old Ashya King say cured him of brain cancer, destroys cancer cells directly, leaving healthy tissue virtually untouched unlike in chemotherapy.