Helga Moddansdttir's sibilings were Angus the Generous and sisters Frakkk and orleif, all four children having both Norse and Gaelic names as their father was Celtic and their mother was Norse.
Whatever their origins, in addition to the titled Otarr, Helga's siblings were, Angus "the Generous" and her sisters Frakkok and orleif. These children had both Norse and Gaelic names, whereas Orcadian families tended to have exclusively Norse names. It is thus likely that Helga's ancestors were of mixed heritage with her father being of Celtic origin and her mother possibly having a Norse background and related to the jarl Ottar who was killed in 1098 fighting in Man. 
