I noticed that in the description of Haurchefaunt's painting, his full name is revealed as "Haurchefaunt Greystone" instead of Fortemps. I assume this is because he is illegitimate.
Does Greystone come from his mother's side, or does this mean that there is a ASoIaF-style system of naming bastards like "Snow" and "Rivers" and Greystone is a reference to a bastard born in Ishgard city. If so are there other lore-accurate bastard surnames?
Edit - we have received the answer: