The ending doesn't make sense? Spoilers Farseer & Tawny Man

[Omie]

I think the relationship between Fitz and the Fool turned out like the relationship between Fitz and Nighteyes would have if Nighteyes had decided to join a wolf pack and find a mate. The fact that Nighteyes never did either turned out to be beneficial to Fitz in many ways, but it left Nighteyes living a life that was only half-wolf. He didn't complain, because he didn't see it that way (he didn't care about what he was 'supposed to be', only what he was) but the life he could have lived is still a life lost. I think the difference in the relationships is that Fitz did ultimately find his own 'pack' (Molly, her children and his new life). The Fool had to find the strength to let him go (whether you think it's strength is up to you. It could simply be that the Fool knew he would not be strong enough to watch Fitz live his own life separately and then die of old age while the Fool was still in his prime) because he knew that as long as he was there he would be too strong an influence in Fitz's life when Fitz's life would be happier as Molly's husband and Nettle's dad rather than as the Catalyst. If you remember back to when Nighteyes tried to live with a pack for a time, he told Fitz that he would come running if only Fitz asked it of him. Fitz had the strength not to ask. I think the Fool sees himself as a bit of a toxic friend to Fitz.

Having said that, I think there's wriggle room for the pair to pair-up again, or at least to influence each other's lives from afar, but that depends on whether Robin Hobb is stuck by a plothammer that causes her to write about them both or either one of them separately.