Domnall mac Ailpín, Rí na Dál Riata - Merge?

cf Giric I mac Dúngail, king of the Picts or king of Alba and Kenneth I Mac Alpine, king of the Picts

Here was why they weren't merged previously:

Firstly
"Giric isn't the son Of Donald, but a rival king to one of Kenneth son's Aedh, as far as primary sources found here show: https://fmg.ac/Projects/MedLands/SCOTLAND.htm#KennethIIIB:
GREG [Grig/Ciricius] (-Donedoure [892], bur [Isle of Iona]). The 10th century Pictish Chronicle Cronica de Origine Antiquorum Pictorum records that, when "Eochodius…filius Run regis Britannorum, nepos Cinadei ex filia" succeeded King Aedh, "others say" that "Licet Ciricium filium" reigned[24]. The Cronica de Origine fixes the chronology by adding that "Aed filius Neil" died in the second year of his reign, and that there was a solar eclipse in the ninth year, adding that "Eochodius" was expelled from the kingdom. The Annals of Inisfallen and Annals of Ulster record the death of Aedh son of Niall King of Ireland (see the document IRELAND) in 879 of "Aed son of Niall king of Temuir”[25], which would place the accession of GREG King of Scotland to [877]. The 12th century Cronica Regum Scottorum lists "…Hed filius Kinet i anno, Grig filius Dunegal xii…" as king, dated to the 9th century[26]. No information has yet been found to identify his alleged father "Licet". However, a different indication of Greg’s parentage is provided by the 11th century Synchronisms of Flann Mainistreach, which name (in order) "Cinaet mac Ailpin…Domnall mac Ailpin, Custantin mac Cinaeta, (Aedh mac Cinaedha), Girg mac Dungaile, Domnall Dasachtach (mac Custantin)" as Scottish kings, dated to the 9th and 10th centuries[27] The Chronicle of John of Fordun, presumably echoing the Synchronisms, records that "his brother Heth the Wing-footed…also a son of Kenneth the Great" succeeded King Constantine and reigned one year, although "according to the rule of the kingship Gregory son of Dungallus should have come before him", adding in a later passage that Gregory succeeded as king in 875 after Aedh died, and reigned eighteen years[28]. The chronology suggests that "Ciricius" and "Gregory" refer to the same person. If these sources are being read correctly, Greg and Eochlaid ruled at the same time, presumably as rival kings probably over different parts of the country. If the mid-14th century John of Fordun can be believed, Greg had a better claim to the throne than King Aedh. This would suggest that he was a member of the same family, maybe in the previous generation. The Chronicle of the Scots and Picts dated 1177 records that "Edh mac Kynnath" reigned for one year, was killed "in bello de in Strathalun a Girg filio Dungal" and that "Girg mac Dungal" reigned for 12 years, died "in Dundurn" and was buried "in Iona insula"[29]. The Chronicle of the Picts and Scots dated 1251 includes the same information[30]. The Chronicle of John of Fordun records that "King Gregory died after a vigorous reign of eighteen years, all but a few months…at Donedoure" and was buried "in the island of Iona"[31].

Secondly,
Donald is the son of Alpin according to John of Fordun, but Anne Brannen disagrees:
[ALPIN (-killed in battle against the Picts in Galloway [20 Jul/Aug] 834). The Chronicle of John of Fordun records the accession of "Alpin the son of Achay" in 831, his reign of three years, and his defeat by the Picts "20 July" after which he was beheaded[14]. The 12th century Cronica Regum Scottorum lists "Alpin filius Eochal venenosi iii, Kynedus filius Alpini primus rex Scottorum xvi…" as kings, dated to the 9th century[15]. It should be noted that Alpin’s parentage is not stated in the earlier chronicles.] m ---. The name of Alpin's wife is not known. Alpin & his wife had two children:

i) KENNETH [Cinaed] MacAlpin (-Forteviot, Perthshire 13 Feb [858], bur [Isle of Iona]). His parentage is confirmed by the Annals of Ulster which record the death in 858 of "Cinaed son of Ailpín king of the Picts"[16]. He succeeded as KENNETH I King of Scotland. Kenneth I & his wife had [four] children:

2. [AEDH (-killed in battle Strathallan [878], bur [Isle of Iona] or [Maiden Stone, Aberdeenshire]).

ii) DONALD [Domnall] (-Kinn Belachoir palace or killed in battle Scone 13 Apr [863], bur [Isle of Iona]). The 10th century Pictish Chronicle Cronica de Origine Antiquorum Pictorum records that "Kinadius…filius Alpini, primus Scottorum…Dunevaldus frater eius" ruled for four years[17]. The 12th century Cronica Regum Scottorum lists "Alpin filius Eochal venenosi iii, Kynedus filius Alpini primus rex Scottorum xvi, Dolfnal filius Alpini iiii…" as kings, dated to the 9th century[18]. The Chronicle of John of Fordun records that "Donald also a son of Alpin" succeeded his brother in 854, reigned for four years, died "at Scone" and was buried "in Iona beside his brother"[19]. He succeeded his brother as DONALD I King of Scotland. The 11th century Synchronisms of Flann Mainistreach name (in order) "Cinaet mac Ailpin…Domnall mac Ailpin, Custantin mac Cinaeta, (Aedh mac Cinaedha), Girg mac Dungaile, Domnall Dasachtach (mac Custantin)" as Scottish kings, dated to the 9th and 10th centuries[20]. The Annals of Ulster record the death in 862 of "Domnall son of Ailpín king of the Picts"[21]. The 10th century Pictish Chronicle Cronica de Origine Antiquorum Pictorum records that "Dunevaldus" died "in palacio Cinn Belachoir idus Aprilis"[22]. The Chronicle of the Scots and Picts dated 1177 records that "Douenald mac Alpin" reigned for 4 years, died "in Rathinueramon" and was buried "in Iona insula"[23].

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