Hogan/Sullivan

Michael Hogan married Margaret Sullivan in Ireland possibly Nenagh date unknown. One of their children was Martin Hogan & he was born in approx 1868 in Nenagh. Martin's family including parents & other siblings immigrated  to New South Wales, Australia prior to 1903. Martin's NSW marriage certificate states both of Martin's parents, Michael and Margaret, were deceased at the time of his marriage in 1903 to Annie Marcella Schilling. I just cant find a link to the Hogan family in Ireland.

Martin named his residence in Sydney NSW "Nenagh". This is what leads me to believe Nenagh was where the family was from.

Any help would be appreciated.