<human>: Can you condense the text into three sentences or less?

We recently adopted two 7 week old kittens (separate litters).  We adopted Bucky first and we noticed he was very "bitey" with us.  Constantly wanting to bite.  

We ended up adopting Izzy so he could have a friend and we read that it sometimes helps with the biting when you have 2.

Well, now Bucky just takes out all his attacks on poor little Izzy.  She wails and "meows" loudly when he jumps on her, yet won't really defend herself.  She just takes it or runs from him.

Is this normal?  Should I just let it continue and see how it plays out?  Or should I intervene when this is happening?
<bot>: Two kittens, one is an asshole.  One is too submissive and won't defend herself.  What to do?