The 1861 Census refers to an earlier child, Louisa, born in 1845,although I haven't been able to find her birth on GRO.

I have found another Pugh with the mother's maiden name of Jellamy - Mary Ann born in Abergavenny in 1843 (Volume 26, page 48).

I haven't managed to find them in 1851, although it took me a long time to find them in 1871, especially as their surname was different.