A Complicated Lineage

I've been puzzling over Galahad's lineage. On Grail 33 Bors is convinced Galahad is the son of "the Fisher King's beautiful daughter." This is reinforced by Galahad's brief mention of his relationship to the Fisher King on Grail 37: "'...my uncle, King Pelles, and my grandsire, the Rich Fisher King.'" Again on Grail 39 Gwenivere is convinced that Galahad is "the son born to Lancelot by the daughter of the Rich Fisher King." All of this becomes very complex, though, when on Grail 46 Galahad convinces "the queen that he [is] the son of Lancelot and of King Pelles' daughter." Wait. I thought Pelles was his uncle. And his grandfather isn't Pelles, but the Rich Fisher King, who, if we give any credence to Grail 37, is the father of Pelles. Somewhere the two have become conflated. And I've become confused. Has anyone else?

This is all the more complex when one considers Galahad's relationship to Joseph of Arimathea. Grail 37 alludes to Galahad as "he who stems from the noble house of King David and the lineage of Joseph of Arimathea," but Grail 60 mentions Galahad as "the last of Nascien's line." Curious. Because Nascien and Joseph aren't related. Nascien is brother to Mordrain (Evalach of Sarras, post-his-baptism), and according to Grail 58-59 Joseph is simply the Christian who happened into Sarras and proclaimed the evangelion. In other words, Joseph and his son Josephus aren't blood relatives of Galahad.

So there are a couple of stunted branches in Galahad's family tree. Anyone have any idea how these could be ironed out?