I'd like to start by saying that I'm sorry............
If your doggie is getting on in age and perhaps doesn't see or hear well, then your family runs a risk. If someone startles him, they may end up being attacked.
We had a border here at work (my boss') and when he got up in age (16) he became hard of hearing, had cataracts, and was actually getting senile. One evening, out of the blue, my boss was on the couch watching TV and "something" happened to Josh. He got up, ran over to boss, and bit him on the face (nose). It was like he was possesed.
He was kept isolated (from their other 5 dogs) and watched carefully. Went downhill. Started "getting lost" in the yard and freaking out pretty often.
You have to honestly and carefully look at the possibility that he is becoming a danger to his family.............
They don't know the difference between right and wrong when they are startled, they just react.