burke and mcredmond families

I am looking for any information about the backgrounds in Ireland of my great grandparents Richard Burke and Mary McRedmond. 

I am not sure when they came to Australia (can't find them on shipping lists) but they married in Melbourne in 1861. I have following details about their birth. 

Richard Burke

Birth 1836 in Rathmore, Offaly,  Ireland

Parents John and Ann nee Walsh

Death 14 Dec 1909 in Killaloe Station, Eulo, Queensland, Australia,

Mary McRedmond

Birth 1843 in Rathmore, Offaly, , Ireland

Parents Michael and Mary nee Walsh

Death 2 Oct 1888 in Sydney, , New South Wales, Australia

I have found documents in Australia that show Richard sponsored Mary's older sister to come to Australia and she arrived 1858. The documents show Johanna's age as 19 and her  birth as about 1839, her parents were Mary  (dead) and Michael (alive) and that she had a sister Mary in Sydney. At this time Mary would have been about 15 but knew Richard then 22, 3 years before their marriage. Her place of origin was Birr, her referee in Birr was the parish priest and she was a domestic servant.

Subsequent documents show in 1863 Johanna sponsored William Hoolan aged 25 from Parson's town Birr. He was a labourer and referee in Birr was Mr Edward Sing (i believe the correct spelling is Synge) from Rathmore Kings Co.

Johanna later sponsored her younger sister Kate but she declined to take up the offer and may have remained in Ireland. Kate was born about 1854 so was very young when the other 2 sisters left Ireland.

I don't know anymore than that. My grandmother told us when we were very young and didn't ask questions that her father was a groomsman at a castle and that he ran away with her mother because she was of a better class. 

I am hoping to visit Ireland in 2013 and would be interested to know any information about these families or places to investigate further.