Duncan of Caithness

married Groa Thorsteinsdotter

father of Grelod

http://fmg.ac/Projects/MedLands/SCOTTISH%20NOBILITY.htm#GreladCaithnessMThorfinnIOrkney

DUNGAD [Duncan] . Mormaer of Caithness.

m GROA, daughter of [THORSTEIN "the Red"]. Dungad & his wife had one child:

a) GRELAD . Snorre names "Grelad, a daughter of Earl Dungad of Caithness…[and of] Groa, a daughter of Thorstein Raud" as mother of the five sons of Thorfin "Hausakljufer"[59].

m (941) THORFINN "Hausakliffer/Skullcleaver" Jarl of Orkney, son of EINAR "Turf-Einar" Jarl of Orkney & his wife --- (-soon after 977). He appears to have become Jarl of Caithness.

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The Mormaer of Caithness is not the same as Mormaer of Atholl:

http://en.wikipedia.org/wiki/Mormaerdom_of_Caithness

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His name is preserved in Duncansby Head (profile pic) Ross, David: ‘Ancient Scotland’, Geddes & Grosset, Scotland 2004. _____________

Duncan and Grelad had one daughter, Groa. She married Thorfinn Hausakljufr (the skullsplitter), Earl of Orkney. Thorfinn succeeded as Mormaer of Caithness. After this, the Mormaerdom of Caithness was in the hands of the norse Earls of Orkney.

Skuli Thorfinnsson, son of Thorfinn and grandson of Duncan had the mormaership of Caithness confirmed by King Kenneth II of Alba.