Do you have any quests in Eastmarch by any chance?
Yes, a quest called "dear cousins"
And havent done most of the eastmarch quests with that character
That quest is to bring news of his death to his family. You obviously didn't do that, and he haunts you until you do.
Damn I have to start that quest on all my Characters, I remember one from ad, I think in auridon where if you had the quest a voice would comment when you killed. Can't remember exactly.
Moons and sands shall be your guide and path.
PC EU/NA