Very minor nitpick. "Einarsson" is a patronymic derived from a parent's given name, not a surname or family name as is common in many western cultures. In the case of the article, Einar is a common Icelandic given name [1] that both victims fathers shared.
The Icelandic naming system [2] is interesting. Basically, children get a given name plus a patronymic (father's give name with son or dóttir suffix) or matronymic (mother's given name with son or dóttir suffix). So people two generations apart in the same family have completely different names, and non-siblings having the same patronymic isn't an indicator of kinship.