The incredible donation
After 11 weeks in the hospital ward, Grainne took her son home to Drogheda, Co Louth in December 2017.
Grainne said: "He cannot walk and is fed through a tube, he has the nasal tube since September.
"I’m trying to get money to get him to a private consultant who will look after him medically and fit the tube in his belly."
Grainne set up a Gofundme page in the hope of raising €10,000 for her son's care but couldn't believe when UFC star Conor McGregor donated this week.
She told Dublin Live: "Conor has made our dreams come true in so many ways, and I can verify it wasn’t for a publicity stunt, he privately donated to us, I just had to let him know how much we appreciate it."
In a private message to Grainne the fighter wishes Bru the best of luck and wished him a full recovery.
He said: "Best wishes and hopes for a speedy recovery for Bru. From Conor, Dee and family."
The money will help Bru get the care he needs to make a recovery from his illness.
The Gofundme page remains open if you wish to donate any money to help the family.