I am at my wits end with the oldest twin. For the last couple of months she has been on a biting frenzy with her twin who is currently covered in at least ten bite bruises. I have tried everything, and I mean everything that has been suggested to me by people who've had biting issues. I thought I would bring this to the twin board, hoping that other twins have had these issues and they've been resolved. They are 17 months old. She has only ever tried to bite one other child, one of my friend's twins when he took something she wanted, go figure. This is getting super old and my poor younger twin is bit up to pieces by her bullying sister. My oldest never bit so this is all very new to me and I'm very through with it. Thanks...
We had the same thing with our kids although they were a bit older. Other than vigilence and time, I'm sorry to say nothing worked. I ended up keeping the 'biten' up on my hip while the biter was in her 'mood'.
It's hard and I'm sorry I don't have more helpful info. Like you we tried everything even to the point of giving the biten the permission to bite back which he never did. It was just part of their dynamic and their stages and it was exhausting.
The only good thing I can tell you is that it will end someday soon.
When my girls were that age, first one was the biter, then a few months later the other became a biter. It just took time for them to get it out of their system I guess. Then ds came along. He's almost out of the biting stage. When he bit his sisters I would tell them that they used to bite too and they couldn't believe it.
Hope it ends for you soon!