At what age does it become unacceptable to physically fight siblings?

🌹C

So I know siblings fight. Lord knows my sister and I physically beat each other as kids / teenagers.

I don’t know if anyone saw the clip from kourtney and Kim kardashian on their show physically fighting, but the two of them are like 40 years old with kids. Just got me thinking, at what age do you think physical fighting between siblings is totally unacceptable?

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