Hello..
It may have been possable..as I know many from Ireland also went to Australia..I'm sure that my Great X 3 Grandfather had siblings..and I have no idea where they may have gone..as well as Frances Moran...my Great X 3 Grandmother..she must have had siblings as well..and have no idea about them..
One thing that I did find out..is that John Cullinan & Frances (Fanny) Moran were married on January 10, 1847 in St.John New Brunswick Canada...so that at least answres that question..
Regards
Frederick Perry