Should marriages allow more partners?

Sure, why not. It exists in the world and should be available for storytelling. I didn't know Vlad Dracula has three wives lol. Stealing is illegal too. Just because I play as a klepto sometimes and steal things in the game, doesn't mean I steal in real life. I actually know of someone who was married, then he went to the united states for work and fell in love with someone else without telling her he is already married. She proposed to him and he said yes and got married to her, without telling her about his wife in Canada. When he came back to Canada and returned to his wife with plans to eventually relocate to America, but he was too scared to tell her he met someone else and married her in the states, then he couldn't decide who he wanted to be with. So in fact, he was actually married to two women for several years, until one of his friends outed him and they both broke up with him lol. I could totally see Don Lothario ending up with two wives in different worlds in a similar story...