Sims 4 Multiplayer Mod
Not sure if people are aware of this, but there was a mod created that allows you to play with another friend in the same household. It's called SimSync. Here is the official website: https://simsync....
Forum Discussion
James Turner and Dr. Gluon have been running a sporatic let's play of the mod over the last couple of weeks. It's interesting, but there are too many caveats, I feel, for wide spread use.
