Is this the 1881 census you mention ?
Owen Thomas 42 mason born Liverpool
Sarah Thomas 38
Sarah Ann Thomas 19
Owen Thomas 16
Hugh H. Thomas 15
Elizth. Thomas 12
Richard Thomas 10
Catharine Thomas 8
Mary E. Thomas 6
Margaret J. Thomas 4
RG11/5594/ 27 p47
There's a possible passenger list :
Owen Thomas 52
Richard Thomas 20 both described as labourers
dep 28 Jan1891 Liverpool to New York on Teutonic
In addition there's a marriage for Richard Thomas to Minnie Cornell 11 Aug 1911 Monroe , NY
parents Owen Thomas and Sarah Hughes.
The above fits with Owen Thomas , stonemason , who married Sarah Hughes 5 Jan 1861 Holyhead.
Is this your family ?