Domnall mac Caustantín
Domnall mac Caustantín is thought to have been king of Dál Riata in the early ninth century.
Domnall's existence is uncertain, and is based on attempts to reconcile eleventh century works such as the poem Duan Albanach and the Synchronisms of Flann Mainistrech with the evidence of the Irish annals.
The Duan says that Domnall reigned for twenty- four years and places him between" Aodh", Áed Find, and the two Conalls, Conall mac Taidg and Conall mac Áedáin.
Flann gives Domnall's father's name as" Constantine".
The only person of that relatively uncommon name known is Causantín mac Fergusa, king of the Picts from 792 to 820.
Since Áed Find died in 778, and his brother Fergus mac Echdach was king of Dál Riata at his death in 781, it is thought unlikely that Caustantín's son could have been king as early as 781.
Additionally, a king named Donncoirce is reported to have died in 792, and Conall mac Taidg died in 807, making it very difficult to accommodate a 24- year reign at this time.
Since no kings of Dál Riata are known for the period from 811, when the four- year reign of Conall mac Áedáin is presumed to have ended, and the four- year reign of Áed mac Boanta who died in 839, Domnall mac Caustantín may have been king from around 811 to around 835.
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Conall mac Fidhghal
Conall mac Fidhghal, 24th King of Uí Maine, died 782.
Conall mac Taidg
Conall mac Taidg( died c. 807)( Conall son of Tadc) was a king of the Picts from 785 until 789.
Very little is recorded of Conall.
He is mentioned twice by the Irish annals, the most reliable source for the history of northern Britain in the years around 800.
He also appears in later king lists.
Comgall mac Domangairt
Comgall mac Domangairt was king of Dál Riata in the early 6th century.
He was the son of Domangart Réti and grandson of Fergus Mór.
The "Annals of Ulster" report his death in 538, 542 and 545, the "Annals of Tigernach" in 537.
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Duncadho mac Duib Da Tuadh
Conall mac Fidhghal, 25th King of Uí Maine, died 782.
Conall mac Comgaill
Conall mac Comgaill was king of Dál Riata from about 558 until 574.
He was a son of Comgall mac Domangairt.
It is said that he gave Iona to Saint Columba.
The Duan Albanach says that he reigned "without dissension", but there is a report of an expedition by Conall and Colmán Bec mac Diarmato of the Southern Uí Néill to "Iardoaman" in the Annals of Ulster for 568.
The much longer entry in the later and less reliable Annals of the Four Masters reports: "A sea fleet was brought by Colman Beg, son of Diarmaid, son of Fearghus Cerrbheoil, and by Conall, son of Comhgall, chief of Dal Riada, to Sol (Seil) and Ile (Islay), and they carried off many spoils from them."
The Senchus fer n-Alban says that Conall had seven sons: Loingsech, Nechtan, Artan, Tuathan, Tutio and Coirpe.
However, Connad Cerr is taken to be a son of Conall, and the death of Conall's son Dúnchad, is noted in the Annals of Ulster and the Annals of Tigernach, leading the army of the "sons of Gabrán" in Kintyre.
Conall mac Áedáin
Conall mac Áedáin was a king in Scotland in the years around 800.
It is thought that he was a king, or sub- king, in Dál Riata.
He is mentioned once in the Annals of Ulster, for 807, when he defeated and killed Conall mac Taidg in Kintyre.
Conall is thought to be mentioned in the Duan Albanach:" The two years of Conall of glorious career, And the four of another Conall."
The first is presumed to be Conall mac Taidg, the second Conall mac Áedáin.
His reign is therefore reconstructed as beginning in 807 and ending in about 811.
He is thought to have been followed by Domnall mac Caustantín.

Question: Who is Conall Mac Comgaill's paternal grandfather?
Answer: Domangart Réti