I just figured out my Sim is married to another sim but in a growing relationship with a new Sim. I am doing Missed Connection and have her and the new guy at level 9. Before proposal would not be an option until she divorced the first sim. SO I socialized with him, chose a rival action and did something mean then it gave me the option to divorce. Once that was complete, immediately the proposal option with the new sim was available. Apprantley, polygamy is not an option in Sims Mobile but hopefully that will change 😏