The kings of Moylurg were a branch of the Síl Muiredaig, who were themselves of the Uí Briúin Ai who descended from the Connachta.
Maelruanaidh is said to have made a deal of some nature where, in return for abandoning any claim to the provincial kingship, he would be given Moylurg.
This royal connection was exploited to oust the existing chieftains of Moylurg, the MacReevys (Irish: Mac Riabhaigh, later anglicized spelling McGreevy).
There are very few clues as to the exact point in time when the MacRiabhaighs (MacReevys/McGreevys) were dispossessed of their ancestral lands by the McDermots or to a controversy which precipitated the action.
The statement on the McGreevy Stone in Ardcarne Cemetery (erected in the 20th century, c.1930) that the MacRiabhaighs (MacReevys/McGreevys) were "kings of Moylurgh ... until 1255" may be the most reliable, and also is consistent with the statement by the Irish genealogical authority Edward MacLysaght ("More Irish Families") that the McGreevys were "lords of Moylurg ... until the 13th century, when they were subdued by, and become tributary, to the McDermots".