Giving names was a big issue at the camp as there was a concern about some men being eligible for military service. This continued right up to the time they were released at the end of December 1916. It was one of the background issues that contributed to the camp doctor committing suicide (he wasn't supposed to give aid to men unless they gave their names). You may find UK records limited as a result.
if the UK records don't yield anything, the Irish records might.
Do you know if he survived to write a Witness Statement for the Bureau of Military History?
NLI has quite a few Fron-Goch resources
My wife's gt uncle, William O'Brien, died shortly after his release from Fron-Goch in November 1916. His name was brought up in the Commons
His brothers were "out" causing mischief in 1916 but were not amongst those arrested. They were both active all the way to the Civil War. I've not found any info about the 3 of them to date in any UK archives other than the above Hansard entry.