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 ?