The Fool (spoilers for all RotE books, including LST)

[Lady Persephone]

I don't have much to add except that I love the fact that we actually finally got an explanation for something that at the time just felt like a bit of an intentional mystery ("two cousins as fathers... as is the custom") in the background of a mysterious character that would probably never be resolved. I remember it has generated some speculation over the years (does it mean simply that the custom was for three people to raise children? Does the custom demand the fathers to be cousins specifically or can they be unrelated?  Are they both biological fathers? How does that biology work etc?) but it never seemed like it really mattered for the story what the answers were. But here we are, all these books later and that old little mystery has become a major plot point! 

It seems to me that based off of how we get Bee from Fitz and the Fool sharing such a strong bond, I don't believe two men have to be related, but I do think they have to share a strong bond with each other.  It probably helped for the Fool's two fathers to be related, such as cousins, because they probably shared a strong bond already, blood being thicker than water and all that.  In the case of Fitz and Fool, they were bonded in so many ways to mingle the stuff of their beings.  Neither of them could deny (even homophobic Fitz *lol*) that they loved each other.  That love was so strong that we can see how it affected them both throughout the books, most poignantly during the Golden Fool and Fool's Fate where we see Fitz longing to spend time with Fool and unable to simply let him die.  At the end of FF, half of Fitz wanted to follow the Fool and be by his side forever and likewise half of Fool wanted to return with him and never leave his side--had circumstances been different and had Pilkrop minded his own damned business (sorry sorry, I was so upset with him, even if there was a logic to it).  It wouldn't have worked for Fitz to have followed the Fool because Bee would not have been born.  If the Fool had stayed with them, he could have watched Bee come into existence and so much turmoil could have been avoided, but Bee's fate would have been changed and certain prophecies wouldn't have been fulfilled. So it had to work out this way.  

Are they both biological fathers? How does that biology work etc?

Good questions!  I think they are both biological fathers, contributing to the fertilisation of the egg.  How that biology works, well, how do Elderlings come to be Elderings?   Some of the dragon's being is infused into a human.  How does the white rose get some of the red rose's tinge?  They grow so close together, the stuff of their beings get mixed.  It's hard for us to understand it because it's not possible for us as humans.  

Everyone's spent all the time arguing about the Fool's gender and sexuality when none of that actually mattered.  It didn't keep the Fool from producing Bee with Fitz, after all, and we needed Bee to come into existence to tie everything together.  She wound up tying together all the plots from all the trilogies there at the end.   And no doubt she shall continue to change the world.  She might not even need a catalyst.  I think she might be both--White prophet AND Catalyst mixed together as one.  Think of it!  She is the product of a White prophet and his Catalyst after all.