Complex sentence: By the 14th century an O'Tuathail (O'Toole) (of the Uí Dunlainge) had established themselves as lord of Ui Mail, having been in their turn been expelled from south Kildare by the Norman incomers.
Split into simpler sentences: By the 14th century O'Tuathail (O'Toole) (of the Uí Dunlainge) had teken the lordship of of Uí Máil. They having been in their turn been expelled from south Kildare by Norman incomers.