Edward OWENS & Sarah COULTER are my g3-grandparents.
Edward was from Julianstown, Meath; his parents were Simon OWENS of Julianstown, & Christina MCGOUGH (of Dublin?). Sarah was from Dundalk, Louth; her parents were Joseph COULTER of Dowdalshill, and Jane IRWIN.
Their first child Jane Margaret (my g2-grandmother) was born 1839 in Castlebellingham, Louth. Edward was on the voters list there in 1842. I don't yet know where the other children were born, except as you say, the youngest Samuel Arthur Wellington OWENS was born in Trim, Meath c1855.
Though I have seen the 1862 date before, they actually emigrated on the Saldanha's 1863 voyage, not the 1862 (according to a passenger list in the Qld State Archives).
I have a fair amount of info, some solid and some a little more rubbery! Please contact me if you wish to share research - I'm very happy to do this, and keen to get in touch with OWENS relatives.