When Tyrion is asking Lord Tywin why Robb would be stupid enough to throw away the Freys for Jeyne, his father replies:
However, the only information we have about Jeyne's mother comes on the previous page:Jeyne Westerling is her mother's daughter and Robb Stark is his father's son.
Gawen (Jeyne's father) is a good man but his wife is Sybell Spicer.
So, given that this is all we know about Lady Sybell, what does it say about Jeyne that she could be described as "her mother's daughter"?Lady Sybell's grandfather was a trader in saffron and pepper, almost as lowborn as that smuggler Stannis keeps. And the grandmother was some woman he'd brought back from the east. A frightening old crone, supposed to be a priestess. Maegi, they called her. No one could pronounce her real name. Half of Lannisport used to go to her for cures and love potions and the like.
Also, when Tyrion asks why Lord Westerling would betray House Lannister, and did he not remember the lessons of Tarbeck Hall and Castamere (other houses to try and betray Lord Tywin, they were both subsequently ruined by him), Lord Tywin responds:
So, were Jeyne or her parents working for Tywin Lannister from the beginning? Did Jeyne seduce him so as to break his alliance with Walder Frey?They are well aware of Castamere, I promise you.
Which lead me to a final question. When Catelyn tells Jeyne that Robb needs a son, Jeyne says that this is what her mother had been saying as well and that she drinks some sort of potion every day to make her more fertile. What if Jeyne Westerling is pregnant with Robb Stark's child?