I wonder if we are seeking the same family line. My g.g.g. grandfather was a Patrick Purtle, born 1818 county Limerick, married Margaret Herreen, 15 children, 12 surviving, some named Michael, Catherine, Patrick, Mary etc. Migrated to Australia in 1840. Patrick's sister Brigid married Margaret's brother Daniel, they also migrated at the same time. Wonder if Michael, Patrick and Brigid were siblings.