There are many choices in the game and most of them are related to political decisions. My favourite thing about the game is that the political side of the game is completely based on reality, there are no absurd choices. I understand that you are uncomfortable with marriage, but actually it would be illogical if it was the other way around, because marriage is the most important act of gaining allies and alliances for royal families to maintain power and legitimacy. Especially when the only son of a king has no heir, this is a big handicap. Some of the reasons for marriage are touched upon in the game. The old king knows that he is at the end of his life and wants to secure the crown for his son, who will take the throne when he dies, so he has both the prince and the princess married to powerful families as a matter of urgency, in order to gain new alliances.