the eldest son ended up in Eglwysilan, Treforest. I traced Eliza from the 1911 census when she was visiting him. There she was 1845 but when I traced her on the 1881 census she was born in Coleford and her eldest son was also born there in 1872 which ties into the Treforest census.
Have no idea of the Abergavenny connection. What is that?