HaR - How old are you anyways? You say you trained your last dog yet it still attacked your brothers, mom and the cats. Obviously the dog wasn't trained or it wouldn't have been attacking.
So you went to the shelter and they gave you a dog that they had just gotten in? Somehow I find that hard to believe. Every shelter is supposed to take in the dog, vaccinate it, test it for temperament and which home's it would do best in, THEN let someone adopt it AFTER they've filled out an application, been asked questions, met the dog, had all the family members meet the dog and see that it gets along with everyone before they adopt the dog out. If you had a problem with the dog you should have brought it back to the original shelter, not a different one.
Did you bother trying to train the dog?
If it was still a puppy there could have been any number of reasons for the nipping, taking stuff, etc. Mainly, lack of training and it was still a pup...IMO.
Was it a male or female? You know only females come into heat, right? And it's not always exactly 6 months apart.
Did you vaccinate the dog? Play with it? Exercise it? Take it to a professional trainer and puppy classes? Have it evaluated by a "good" behaviorist. A good behaviorist doesn't automatically tell you to give the dog up.
What training methods did you use, if any? What was the dogs name...or did you bother naming it?
All breeds have the possibility of biting, agression issues, disliking animals, etc. You have to have a properly bred dog and properly train the dog to become a well behaved member of canine society. Sit, stay, heel, come, give, drop it, down, etc are common commands that need to be taught. You have to teach a pup about bite inhibition (depending on it's age and previous back ground), how to deal with other animals and children properly, to not try to take something that someone else is holding, etc.
It really sounds like you didn't bother training this pup and gave up on it. Tell us what methods of training you used? Why you didn't bring the dog back to the original shelter? How did you introduce your family and the cats to this new dog?
There are so many unanswered questions. It may just lie in the fact that you are new to the country and don't understand English very well yet. The dog may not have understood you either. Maybe you didn't understand the behaviorist and others that were involved. Either way, I don't think you should get another dog any time soon. You are breed biased and don't seem to know how to train a dog. jmo