Ruaidhrí Gilla Dubh Ó Seachnasaigh [SEP] date of death
Ruaidhrí Gilla Dubh Ó Seachnasaigh
Ruaidhrí Gilla Dubh Ó Seachnasaigh Irish Knight and Chief of the Name (died 1569); known in English as "Sir Roger O'Shaughnessy". 
The son of Sir Diarmaid Ó Seachnasaigh, Ruaidhrí was described by Sir Henry Sidney as "a very obedient and civil man, and most desirous to hold his lands directly of your majesty and to be delivered of the exactions of both the earls of Clanricarde and Thomond", whose earldoms lay north and south of O'Shaughnessy's small lordship. 
The
John Ó Seachnasaigh
John Ó Seachnasaigh, Chief of the Name, died 1601.
Ó Seachnasaigh was the eldest but illegitimate son of Sir Ruaidhrí Gilla Dubh Ó Seachnasaigh. Upon the death of his father, his younger but legitimate half-brother, Sir Dermot Ó Seachnasaigh, inherited Cenél Áeda.
Contention between the two brothers continued till 1585, when they both travelled to Dublin to attend the 1585 Parliament. It seems that the parliament found in favour of Sir Dermot, which left John destitute. However under Brehon law