Catholic Encyclopedia: Saint Donnan

Three or possibly four Irish saints of this name lived in the sixth and seventh centuries. St. Donnan of Eigg and St. Donnan of Auchterless are probably the same person. There was also a St. Donnan the Deacon, blood brother of St. Kieran of Clonmacnoise; and a St. Donnan who was a nephew of St. Senan and who succeeded St. Kieran of Clonmacnoise as Abbot of Aingin.