@drogosnextwife i am certain this will be horrifying, but my mother did this and it worked quite effectively.
When a child (little, not older) bit her, she bit them back. Just enough to hurt. If they hit her she hit them back, only enough to sting, but enough for them to understand how they were hurting her.
She would first say "no" "dont" "stop" etc. But if they wouldn't, she gently, without anger, bit back. She said it never took more than that one time.
She was eldest of 6 children and babysat many cousins as well as our sets of children. I don't think she did it to mine, but i did to my daughter. It wasn't a CHOMP! it was warnings then "this is how it feels "
After that, if she hit me, i would rub my arm and say in hurt voice, "ow! You hurt me." Her: "I sorry." Would be the reply.
My children aren't now, as adults, physically abusive, and as children, aside from that early stage they go through, not hitters or biters.
My son remembers timeouts and said he understood and decided to avoid them by being good.
Dd??? She's still a holy terror! Couldn't give her a time out bc she was dangerous! Couldn't leave her alone! She was always a challenge. I once threatened to spank her favorite teddy bear and she got so upset i couldn't even punish her toy!
Every child is different.
The people who say, "i treated both the same, etc." Are missing the point that everyone is different.
I