In chapter 5, if you romanced Triss the king inquires as to the nature of the relationship. I chose the 1st option which was we are close and its no one else's business. The king's reply was: no need to be rude, I too loved Adda's mother, they forbade me from marrying her but I hope you fare better, at least you are sterile so there is no chance of you having children. Adda's mother was Foltest's sister (the degenerate). This made me wonder whether Trissy is in fact Geralt's sister (and how would his royal highness know?). There are some convoluted legends told through in-game literature and tall tales that give some vague hints but nothing specific. Any ideas?
Perhaps it's a translation issue but it definitely raised some questions for me. Also, Sapkowski's world is nothing if not gritty if The Witcher is any indication and doesn't shy away from illustrating extremes of human nature.
As far as I know, it's never even hinted at in the books. Moreover, it would be strange that Foltest would know if they were brother and sister, and nobody else does. If anybody else does, why don't they say anything about it? I can easily imagine Shani bringing up the issue.
