About us
The results to date (as of June 2026) for the members with a Donnellan (or any other spelling variant) surname allow us to classify the members into the following five groupings.
Lineage 01: Members with ancestors from County Longford (R1b-ZZ87 positive, likely descendants of Niall of the Nine Hostages, died in 5th century AD)
There is a significant cluster of Donlons (who all use this spelling) in County Longford. Members classified in this group have ancestors from Derryshanogue, Cashel parish, or Moydow parish, County Longford, or have Y-DNA that closely associates them with these. The members with ancestors from Derryshanogue, Cashel parish and Moydow parish have a common ancestor that lived about 1500 AD (the estimated date of occurrence of their most recent common SNP).
It is not clear who the progenitor of this lineage is.
Lineage 02: Descendants of Dómhnalláin, progenitor of the Donnellan clan (R1b-FGC5939 positive, likely descendants of Eócháda Tírmchárnai, died 558 AD)
The main Donnellan clan that lived in Ballydonnellan Castle, Ballydonnellan East, Killalaghtan Civil parish, County Galway is said to descend from Dómhnalláin, who lived around the 900s. Our project is very fortunate to have a member descended from the Killagh branch of this family with a family tree extending back to Dómhnalláin. He has taken the Big-Y test, so we can correlate the Big-Y results with the ancient Irish genealogies.
The Y-DNA results show that this Donnellan family initially belonged to the Uí Bruin Aí tribe. However, later they became associated with the tribe of Ui Maine (or Hy Many), whose kings were from the O'Kelly clan.
There is a large cluster of Donnellans around Dunmore and Clonbern and Glenamaddy parishes. Many of the members from this cluster have tested positive for descent from this progenitor family.
Lineage 03: R1b-BY198 positive Donelans
There are only two members in this lineage, who have a common paternal line ancestor dated about 1400 AD (from the estimated date of occurrence of their common SNP).
There are several other surnames clustered under the R1b-BY198 haplogroup, in particular Egan, Larkin, Dunn, and Curley. These all originated around the same general area of eastern County Galway.
It is not clear who the progenitor of this lineage is.
Lineage 04: Donnellans with County Clare ancestry or R1b-L226 positive
There is a large cluster of Donnellans in the area of east County Clare around Broadford. Recently some members with ancestry from the Broadford area have tested and joined, so it has been possible to identify them as belonging to R1b-L226. This is the haplogroup associated with east County Clare, and with the Dalcassians (Dál gCais) and the O'Brien clan. Conor O'Brien, the present Baron Inchiquin and Baronet of Leamaneh, has been confirmed as belonging to the R1b-L226 haplogroup.
It is not clear who the progenitor of this lineage is.
Ungrouped: Miscellaneous with Donnellan surname or spelling variants
This group includes three members, who do not fit into any of the above lineages at present. One member is R1b-L336 positive. This haplogroup is associated with the Corco MoDruad of Burren in County Clare (see
"High Resolution Paternal Genetic History of Ireland and its Implications for Demographic History", by Tibor Feher). The other two members might still be capable of being allocated to one of the above lineages if they upgrade from Y-37 to Big-Y.
The more members join, in particular the more members take the Big-Y test, the more the big picture regarding the history of the whole Donnellan clan will emerge.