There's a time for negative reinforcement, this is not it. Negative reinforcement only works if it's used constantly to deter an action (invisible fences using shock collars). If your dog gets excited and does things you don't want them to do (pee, nip fingers) the moment they do these things, ignore me, give them no affection, no eye contact, don't speak to them for about 15-30 minutes. Now for the potty training tutorial. 1. Rule of thumb, a puppy can hold its bladder 1 hour for every month of age (2 month old = 2 hours) 2. Take the dog out on that schedule. 3. Stay outside with the puppy and watch them. 4. When they go to the bathroom, praise them. 5. Start early. Good habits are easy to train, bad are hard to get rid of. 6. Try reinforcing a command word for your puppy's different "movements". (The dog pees - "Good girl potty", the dog craps - "Good girl boom boom") After a few months of this your dog will want to use the bathroom outside because they want the praise. If you reinforced the command word, your dog may learn to do their business on command.

You can't beat the shit out of them but you can slap them around a little. I think you probably need to teach your autistic brother a lesson as well.

Physical punishment will teach them, but you have to be very careful to find the midpoint of being too soft that they won't learn, and actually hurting them. Get some pee-pads. We just got a new puppy and we didn't even have to coax him into (usually) peeing on them. Always take your puppy outside when you think they need to pee, and especially immediately after they've peed. This will reinforce the idea that it needs to be done outside (which they will want to do anyway, as they don't like going near their living-space. As it learns to pee on the pad, start moving new pads closer and closer to whichever door you will most likely be taking them outside through. They'll start waiting over by said door when they need to go, letting you know what they need. I've heard that if you always make them 'speak' before you open the door, they'll start barking at the door to let you know they need to go as well, but I didn't have much luck doing that with my last dog.

Give your brother a stern talk about hitting animals and how he should leave punishment to the adults. There's a good chance it'll happen again so keep a close eye on that dog.