On the death of the McGovern chief Giolla na Naomh Mág Samhradháin c.1240, Brian took the chieftaincy.
The Annals of Connacht for the year 1256 state- After the battle of Magh Slécht, Fedlim O Conchobair and his son Aed na nGall, with the men of Connacht, and Tigernan O Ruairc, with the men of Brefne, made an expedition to Loch in Trein; and the two armies fell upon the churches of Brefne, all except Fenagh, and returned to their homes with hostages of the Fir Brefne, that is, of Mac Fiachrach and Mac Tigernain and Mag Samradain and of the son of Art O Ruairc; and Fedlim gave the hostages of the chieftains into the custody of O Ruairc and handed over Mag Samradain to his own son, Aed na nGall.
The Foreigners returned home after this, and the Bishop O'Maicin was 'drowning their candles' about nones, when it was equally dark in field and wood.
[1] The Annals of Loch Cé for 1257 state- A great depredation was committed on Mac Shamhradhain by the people of Aedh, son of Fedhlim O'Conchobhair.
[3] The Annals of Loch Cé for 1258 state- Brian Mac Shamhradhain, dux of Tellach-Echach, was killed by the Connachtmen.