Gerwyn came through the ranks at Ystrad mini and juniors and went on to play school boy rugby at Coleg y Cymoedd. A very promising hooker when he first joined Ystrad 1st XV, he decided upon a positional change and ended up in the back row where he became a strong ball carrying back row forward. Gerwyn played a part in the successful 2016/17 Division 1 league and playoff season, before leaving for Penygraig RFC where he still plays today.