Hi, Mrsh,
Your previous answer is very good.
I do agree that the aggressiveness is what's happening. He has control over your family! You have to gain control over him, and he will be a much happier dog. He won't have to make decisions like this, whether to bite someone or not, or even get mad. Has he been neutered? If not, do that first. It will relieve him of some of the aggresiveness.
I highly recommend a video by Ceaser Millan, a Professional Dog Behaviorist. He rehabilitates dogs, and trains people.
He has his own TV program, the Dog Whisperer, on the NGEO (National Geographic) channel, on Friday nights mainly, but also comes on some other days. This video is available from:
http://www.dogpsychologycenter.com/
I also ordered his new book, "Ceaser's Way", from Walmart online, around $15 US, and it's very good!
There are other good videos available on the web, but this one is really worth your attention.
Another good TV program is on Animal Planet, called Good Dog U. It also shows what to do with aggressiveness.
Please don't think that you are being "mean" to him, if you watch any of the above TV shows, and do what they do. You will establish yourself as "boss", and have a much happier family and dog.
Best of luck.