Pontypool is a town in Monmouthshire which is in South East Wales.
Walter Walsh's birth was registered in Jan Qtr of 1881, in the Pontypool Registration District - Vol 11A Page 134
I cannot see a birth registration for Owen Walsh anywhere at about the right time.
I can't find any likely matches in the 1881 Census in the UK.
You can use the registration details listed above for Walter to purchase his birth certificate direct from the General Registry Office (GRO) at a cost of £9.25. His birth certificate will tell you when and where he was born, the names of his parents, and his father's occupation which might help finding them.
The GRO web site is https://www.gro.gov.uk/gro/content/certificates/Login.asp