Recently we got new kittens in addition to the three, one 6 yr old and two 5 mth old cats, of course at first all was tense but all have settled in nicely since. everything seems to be going very well except that the two 5 month old cats keep biting the back of the neck of only one of the new kittens and holding him down. they don't hurt him but they don't let him go until we holler at them. they also don't do it to any of the other cats or kittens. since they aren't hurting him i didn't worry too much about it but just seems weird to me. can anyone tell me why they might be doing this?