

(7) In the next window, select SetRelationship. (6) A window with various options appears select Relationship. (2) Click on Sim D while keeping A active. C and D, and you want A, B and C to be married to D but not to each other (polygynous and polyandrous marriages are like that).

You install the DebugEnabler package in your Mods folder in the usual way (make sure you've got the right version for your game): You can trick the game into letting your Sim be married to more than one spouse at the same time. Make sure to back up your game before trying any of the following suggestions.
