Seeking any information on my GG grandfather Thomas O'Brien born in Dublin in 1837 according to his marriage license. Arrived in Christchurch, New Zealand, in 1875. Upon a few days arrival married Mary Stephenson McKay (Michie) who traveled with her famly to NZ from Glascow on the same boat. A child was born a few months after arrival/voyage. Couple had seven children. Settled for many years in Westport. Thomas trained as a butcher in Ireland but became a "slaughterman" in NZ. On his marriage license and on all of his children's birth certificates the space for naming his patents left blank. No Gedmatch or Ancestry DNA hits to date. Beginning to wonder if he ever knew his real parents and was raised by another or that he was covering up for some past maleficence? Help or insights appreciated.