“How?” asked Cersei.
“By marriage. Yours, to begin with.”
It came so suddenly that Cersei could only stare for a moment. Then her cheeks reddened as if she had been slapped. “No. Not again. I will not.”
[…]
Their brother had been much younger when Cersei wed the first time; he might not acquiesce to a second marriage quite so easily. The unfortunate Willas Tyrell was like to contract a sudden fatal case of sword-through-bowels, which could rather sour the alliance between Highgarden and Casterly Rock. I should say something, but what? Pardon me Father, but it’s our brother she wants to marry?