IV: Sansa as Roose Bolton's bastard.
Sansa hides her smirk as the old maester announces that the Queen and her babe are dead. No one will suspect that it was poison for their Queen was a frail girl whose body was not made for birthing babes.
And if anyone finds out, she knows that no one will accuse her, poor little Sansa Snow, of murdering their Queen, for she was a gentle, soft- spoken and kind bastard girl, the opposite of her rowdy and crazy twin brother, Ramsay.
She owes it to her brother, the poison was Ramsay's idea and the two of them already used it without problems with Domeric, and though people has suspicions that it was Ramsay who killed Dom, no one seems to have the courage to voice it aloud. It secured Ramsay's place as their Father's heir.
And now, it will secure hers as Queen.
She knows that her Father thinks highly of her and wants her to become the next Lady of Winterfell (now the Queen in the North due to war) even if she was baseborn. And he brought her to Riverrun, in hopes that she can catch the eyes of King Robb.
King Robb was a nice man; kind, honorable and just. He was also handsome and strong. He has a good mind in politics and is a great war commander but Father thinks that the King is still a green boy.
She fails at her first attempt to seduce him. He was courteous around her and spurned her advances when she comes to him and Sansa thinks that it is because of her baseborn status. No high lord or King would want to marry or pay attention to a girl like her and she hated being a bastard because of it. But she didn't stop; Robb Stark was hers, only hers.
When he brings back a girl from Crag, Sansa's heart breaks and Father scolds her for not doing her best. But Ramsay, her twin, comforted her and told her that they will find a way and promised her that he'll eliminate the Westerling girl for her to become Queen.
And that evening, when the King was drowned with grief, Sansa comes to him and consoles him for his wife and child's death. She lets him take her maidenhead and when she fell asleep beside him, Sansa smiles, King Robb will probably ask her to marry him knowing that he'll be afraid of angering her Father, Roose Bolton commands half of the Northern army, without him the Starks are lost.