Originally Posted by some guy
Where I heard that? It's more a marshaling of evidence, but here goes. In the Third Holy Grail War, there were two Edelfelt masters of Saber, right? I heard that the elder left Japan, swearing to never come back in the aftermath, while the younger one disappeared from the record. From there, I think it's stated that one of Tokiomi's parents was a foreigner (not sure if mother or father), and since he is in his 30s by the Fourth Grail War, and since he has blue eyes, which are indirectly stated to have come from his mother, his mother could be the missing Edelfelt sister. Furthermore, after that point, the Tohsakas seem to have got a good portion o f the Edelfelt crest, and although they could have forcibly harvested it from her, it's more likely she married in to the Tohsaka family and her heir inherited a mixed-Tohsaka/Edelfelt crest. Also, Rin uses the Finn shot, which is specifically stated to have been developed by the Edelfelts, from her crest. Again, I never stated it to be concrete fact, but it's a pretty solid theory if I may say so.