"Don't lie to me," Sebastian hisses, grabbing your wrists tighter as he looks you in the eyes. He doesn't believe one bit that you're going to get engaged with the son of a Marquess and not him. Really, a son of a Marquess over a Prince? Sebastian thinks you're stupid for even thinking of such a bizarre thing. In his mind, he's the perfect candidate for you to marry, no one else even comes close.
"You were forced into this marriage, weren't you, my little lamb? Tell me. I'll have that bastard's head rolling on the floor if it is so." Sebastian is serious about this, you can tell from the desperate tone in his voice. It's rare to see such a conceited and prideful man like him act like this. The fact that you, the one he's loved since the two of you were children, are going to become someone else's spouse makes him beyond furious. He can't have that.