How old is your puppy? If this is totally new behavior for him, it does sound as though maybe he is in pain from something. Maybe he was bitten by something outside, or maybe you brother unintentionally hurt him while trying to catch him or pick him up.
I would have a vet check him out. Let us know how he is doing, please.
I would have a vet check him out. Let us know how he is doing, please.
