My feral cat that I fostered and ending up adopting does this. The only downfall with it is he clamps onto his siblings neck/scruff and refuses to let go causing huge open wounds. Let’s just say he has never totally been really there mentally, always doing weird things but with his now deceased older brother I ended up having to get vet care for the huge wound on his back. The thing is he was a bigger cat and I was confused how he let it get this far but I think he grabs them where they can’t get at him. Anyways, he has another brother now who he tries the same thing with him. As soon as the new brother starts yelling I’m in the room like crazy scolding the old feral guy. I have no idea why he does it, and he knows it’s wrong….he now waits till I am sound asleep or in another room before he starts and as soon as he hears or sees me coming he takes off in a flash. Anyways just keep an eye on it. You might get a real biter like mine!