Inspirational Ollie Gardener has fallen into unconsciousness, with his family not expecting him to regain consciousness.
Ollie Gardiner, 12 who lives with his parents and brother Theo, 10, in Aston Clinton, was diagnosed with a brain tumour in 2015.
A statement from the family on their facebook page said: "Following a very difficult few weeks and days, I am heartbroken to report that Ollie has suddenly deteriorated further.
"On Tuesday he slipped into unconsciousness and although in the past he has recovered from similar attacks, this time it feels very different.
"He is at home, comfortable in his own bed and surrounded by the love of his family. A team of wonderful nurses are helping us to care for him and he is peaceful and not in any pain.
"Ollie has proved us wrong before, but we have to be realistic.
"We do not expect him to regain consciousness."
The Bucks Herald's thoughts and prayers are with the family at this tough time.