My character is the eldest son of an affluent politician. His family roots run deep, and they are the most powerful family in town. Even though in this day and age arranged marriage is considered archaic at best, this family is very choosy about what gets added to their blood line. That's where your character comes in.
She could be from a poor or wealthy background, but a contract was made with your father when you were just a baby. You've been raised to be a dutiful wife and mother, and of course told you must complete the conditions of the contract. First, you must remain a virgin until your wedding night, and the union must be consummated with the taking of your virginity on the wedding night. Second, you must become pregnant with an heir in three months, with a second to follow.
If you stick to the contract and do your job well, you will be the lady of a powerful household, and your family will be paid a tidy sum. If the contract is broken at any time, you are thrown out on the street with nothing but the clothes on your back.