In this guide. you will find how to change family dynamics (existing sim/family) in The Sims 4.
You need to press Control+Shift+C to open up the cheat box, input “testingcheats true” and press Enter on your keyboard. After that, input “cas.fulleditmode” and hit Enter.
Now click on your sim while pressing and holding the Shift button. Choose the “Modify in CAS” option and you can change the family dynamics of your sims there. Hit the Tick button after selecting them.
