playing any sim

You mean that they don't move away or don't die ?

If you want them to stay in town, you need to turn Story Progression off in your options. They will then only go to work and stuff but not get married, move or have children.

If you want them to not die, you have to turn off aging but that will also affect your active Sim.

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Please accept a solution if your issue is solved. XP is also appreciated.

You know when you have kids and want them to have their own lives but still want to be able to play other family members as well. The options is to make the person moving the active household or not you then are'nt able to play the other family?

You can switch back and forth between households and play them but they will continue to lead their own lives. You can't play them both at the same time.

If you move a Sim out, it's either playing with one or the other but you can switch anytime.

Is that your question ? I'm not sure I understand you right (I'm German speakin).