this mod is about step parents or sibling,
if you like to add drama to your game, or make your adult parent sim marry someone else and make their kids hate it
then this mod is for you.
or you might make the kids like the step parent is also an option
If the new step parent has children and you do too then they might hate hate each other or not
it's your game and you can do anything you want.
More info about this mod
HERE