I am by no means an expert and I’m absolutely interested to see what other people say. However, I would say that neutering can help with male agression. Unfortunatelly, I don’t think it’s as simple as all that. The first worry about bringing a dog into a home with another dog is how they get along in general. It sounds as if your dogs are okay, even if one is a little more rambunctious than the other. Secondly, when dogs, or any animal, for that matter, is brought into the “fold” a pecking order will be established. If you are a firm “pack leader” and neither of your dogs are trying to become alpha male, then the chances for agression is decreased farther. I would advise caution though, becuase, as the previous owner of border collies, I know there is quite a size difference in the two breeds and your pit could injure you BC without intending to, just by playing too rough. Besides, an argument over a favorite toy, or the best spot to sleep, could happen at any time (just like with siblings.) If I were the owner of two dogs I would take the precaution of keeping them apart when you are not home. This isn’t a pitbull specific precaution, just responsible dog ownership. As far as your wifes beliefes, she is right, but it’s not just about loving them, you have to socialize both dogs well and help them build a healthy, brother-like relationship with each other and a child-parent relationship with you (you being the parent.) Again, this isn’t a pit thing, it’s a dog thing. My advice would just be to think logically about the situation and to keep a close eye on the dogs.