That's so sad! Your family has had a lot of unfortunate pets. I understand how you feel - we had two dogs when I was a child, and I was so sad when they died. My sister and her husband had a lovely dog that died after being hit by a car. Her husband also had a dog that got murdered by intruders when he was living overseas. They now have another dog, which I have a special bond with.
Terrible about your brother-in-law's dog too! Dogs are generally only vicious if they've been trained to be vicious or treated cruelly as pups.
I would love a dog of my own, to go hillwalking with, but I would get so upset if it got ill or died.