This would never fly in 2023, but growing up in the mid-1970s (which might as well have been the Pleistocene Age when it came to parenting) there was a dysfunctional house down the street with a single Mom with her hands full with three attractive girls, all step-sisters with each other.
If they started fighting inside the house, the Mom would break them up, then send them outside to finish on the front lawn, and only the winner could come back in for the next hour or two.
By high school, all three were unbeatable as fighters.