Tom and Mary Noble from Enniskillen will be at the Olympic Games to cheer on their son, as will Gavin's brothers and sisters.
Gareth and his wife Maire-Brid will be travelling from Dublin and Sarah-Louise and partner Tristan will be travelling from Liverpool. Meanwhile Marie-Claire and fiance John will be flying down from Aberdeen and Gavin's brother Mark and Hannah will be coming from Manchester.
"We are very excited," commented Gavin's father Tom.
Gavin is among a field of 55 athletes competing in the triathlon that starts at 11am on Tuesday morning.
The swim is in the Serpentine, leading to a 40k bike race passing through the Mall, finishing with a 10k run.
On Sunday night, Gavin will be travelling to a hotel in Hyde Park, having been in a health resort where the Irish athletes are staying. After the race on Tuesday, he will move to the Olympic village.
"He is in great form," said Tom. "He phones us most nights. We are all just very excited," he added.