Question: Who is Fiachnae Mac Áedo Róin's paternal grandfather?

Knowledge 1: Fiachnae mac Áedo Róin
Fiachnae mac Áedo Róin (died 789) was a Dál Fiatach ruler of the over-kingdom of Ulaid in Ireland.He reigned from 750 to 789.He was the son of Áed Róin (died 735) and brother of Bressal mac Áedo Róin (died 750), previous kings.This family had their base in modern-day County Down, Northern Ireland. [SEP] Knowledge 2: Áed Róin
Áed Róin mac Bécce Bairrche (died 735) was the Dál Fiatach ruler of the over-kingdom of Ulaid in Ireland.He reigned from 708 to 735.He was the son of Bécc Bairrche mac Blathmaic, (died 718), a previous king of Ulaid who had abdicated in 707 to become a pilgrim.
Knowledge 1: Fiachnae mac Áedo Róin
Fiachnae mac Áedo Róin (died 789) was a Dál Fiatach ruler of the over-kingdom of Ulaid in Ireland.He reigned from 750 to 789.He was the son of Áed Róin (died 735) and brother of Bressal mac Áedo Róin (died 750), previous kings.This family had their base in modern-day County Down, Northern Ireland. [SEP] Knowledge 2: Bressal mac Áedo Róin
Bressal mac Áedo Róin( died 750) was a Dál Fiatach ruler of the over- kingdom of Ulaid in Ireland.He reigned from 749 to 750.He was the son of Áed Róin( died 735), a previous king.This family had their base in modern- day County Down, Northern Ireland.His father had been slain in battle in 735 by the High King of Ireland Áed Allán( died 743) of the Cenél nEógain and the kingship of Ulaid passed to the rival Dál nAraidi of southern County Antrim.However in 749 the Dál n Araidi king of Ulaid Cathussach mac Ailello was killed at Ráith Beithech( Rathveagh, modern County Antrim) probably in the interest of the Dál Fiatach and Bressal became king.Bressal himself was killed in 750 but the Dál Fiatach retained the kingship.The king list in the" Book of Leinster" places his reign immediately after his father's and state he ruled for one year.This is the chronology followed by the later and more synthetic" Annals of the Four Masters" which state that he was killed at Dun Celtchair( near Downpatrick).The historian Professor Byrne believes that it is probable there was an interregnum in Ulaid between the reigns of Áed Róin and Bressal's brother Fiachnae mac Áedo Róin( died 789).
Knowledge 1: Fiachnae mac Áedo Róin
Fiachnae mac Áedo Róin (died 789) was a Dál Fiatach ruler of the over-kingdom of Ulaid in Ireland.He reigned from 750 to 789.He was the son of Áed Róin (died 735) and brother of Bressal mac Áedo Róin (died 750), previous kings.This family had their base in modern-day County Down, Northern Ireland. [SEP] Knowledge 2: Fiachnae mac Demmáin
Fiachnae mac Demmáin( died 627) was King of Ulaid from 626 to 627.Sometimes called Fiachnae Dubtuinne.He was a member of the Dal Fiatach and nephew of Baetan mac Cairill( died 581) of Ulaid.He was the son of Demmán mac Cairell( died 572).He succeeded his uncle as king of the Dal Fiatach in 581.His first mention in the Irish annals is the battle of Cúl Caíl( possibly Kilkeel, modern County Down) in 601 where he was defeated by Fiachnae mac Baetain of the Dal nAraide.The annals mention Fiachnae mac Baetan went against him so was probably the aggressor.This was part of the struggle of these two rival clans for the overlordship of Ulaid.In 626 was fought the Battle of Leithit Midind at Drung( Knocklayd, modern County Antrim) between these two rivals at which Fiachnae mac Demmáin was the victor and Fiachnae mac Baetan was slain.The annals say the battle was fought by him which implies he was the aggressor.He now becomes King of Ulaid but was himself defeated and slain by the King of Dalriada, Connad Cerr at the Battle of Ard Corainn in 627.The" Annals of Clonmacnoise" claim that this was in revenge for the slaying of Fiachnae mac Baetan.His wives were: Cumne Dub, daughter of Furudrán mac Béicce of the Uí Tuirtri.She was the mother of Dúnchad mac Fiachnai( died circa 644), a king of Ulaid and of a daughter Dub Lacha who married Mongán mac Fiachnai( died 625), the son of his rival Fiachnae mac Baetan.Cumne( Cummíne) Find, daughter of Báetán Cáech of DalnAraide and sister of Fiachnae mac Baetan.She was the mother of Máel Cobo mac Fiachnae( died 647), a king of Ulaid and a son named Suibne.He was ancestor of all later Dal Fiatach kings.6

Answer: Bécc Bairrche mac Blathmaic