My great, great, great grandfather was Patrick Flahavan born in (according to the 1861 Welsh census) in Limerick in 1825. He married Catherine Sullivan (the Sullivans were from Cork). they were in Wales by 1849 when their first son John was born in 1849 in Swansea. However they must have returned to Ireland as my great, great grandmother Margaret (who married into the Irish Gaul family) was listed as being born in Ireland. The only census Patrick is listed in is 1861 and 1871. They seemed to change to the Flavin spelling, possibly to avoid trouble as the Irish were disliked by many Welsh people at this time although his son Thomas listed himself as Flahavin in the marriage records.
I have very limited information as to any family beyond Patrick so if anyone has any links i would love to hear from you. firstname.lastname@example.org