Payton believed that "Muirceartach ... was of some eminence amongst the Cinel Moain, probably the chief of the name, since usually only persons of importance are mentioned in the Annals."
An account of the family was preserved by Dubhaltach MacFhirbhisigh, who recorded that they descended from one Fianbheartach mac Endalaig, a gr-gr-gr-gr-grandson of Niall of the Nine Hostages.
Payton states that most of the Cenél Moen families were driven out of their homeland and east over the Foyle river - "This journey was probably completed by the end of the 13th century, and the O Gormley's, chiefs of the Cinel Moain, thereafter held sway over a territory which extended from Derry to Strabane."
Cenél Moién i c-cionn ráithe iaramh do chur Concobhair mic Conallaigh a toisigheacht, & a c-cennus do thabhairt do Dhomhnall mac Domhnaill Ui Gairmleadhaigh.
Raghnall mac Eachmarcaigh Uí Chatháin do mharbhadh la Cenél Moáin a t-tosach an t-samhraidh-sin cona i n-a dhioghail-sidhe do-rochair Galach Ua Luinigh & Muircheartach Ua Peatain, & as na dioghail bheós do-ronadh in meabail remraite for Cenél MoáinConor, the son of Cu Allaidh O'Loony, assumed the chieftainship of Kinel-Moen; and Donnell, the son of Donnell O'Gormly, was banished from Moy Ithe into Inishowen, to Donough O'Duibhdhiorma.