I picked up the Filial Bonds quest a while ago. I completed some other quests, then decided to locate Torkild. After fast travelling around the random spawn locations for a while I finally located and killed him. I looted the letter and returned to Wulf tocomplete the quest, but I am unable to do so. As soon as I approach Wulf he will comment on how his brother is now with the All-Maker, but does not initiate a conversation. Pressing A to talk to him results in him repeating 'go and avenge him'. The quest does not complete, I am not given any reward and the letter is still in my inventory. If anyone has any ideas or has experienced this I'd be interested to hear about it.

Solved. Had a save where I had located Torkild but not spoken to him. I loaded this, completed the main Dragonborn questline (read the book, defeated Miraak), then approached and spoke to him. After this I was able to return to Wulf and complete the quest without issue.