Hi! I have two kittens, one who is 9 months old and the other who is 6 months old, they are both females, since they became friends the wee one is always trying to suckle on the older ones nipple, she doesn't seem to mind, in fact she lies back and enjoys it. I wonder is it a comfort thing? Or should I try and separate them? This has been going on for almost 3 months now, thanks in advance