I inherited my father's 18 month old English Springer Spaniel when he past away. I basically trained her, since my dad was not physically able to. She had an older "sister", which she lost along with her master, and the freedom of many acres no road and few people. My father had a tough time getting around. So when "Charli" got old enough to challenge the older dog, he couldn't always get there in time to handle the situation the way he wanted. Unfortunately Charli was the one that got punished, mainly with yelling or sometimes put in a separate room, mainly when they ate.
We had lost our dog 6 months before, so when Charli came to our home, she was, (and still is) the only dog. We took it very slow to let her adjust. She was doing well,but 8 months after she was with us my daughter went to pet her and Charli growled, baring teeth at her. She has done this to my husband and 17 yr. old son, but not nearly as often. She has only done it to me when I was grooming her, or the time I tried to put her on her back. I had read about "dominance aggression" and wanted to see if I could put her in a "submissive" position... never did happen.
I believe it is dominant aggression, but it is somewhat selective, and not constant.
We have started with the "Alpha dog" training. Hopefully this will help.
Any suggestions or thoughts would be appreciated. She is a good dog, and we have gotten so attached to her....but my family's safety comes first.