What can I do about separation anxiety of my mini Aussie?

Separation anxiety cannot be dealt with any music or some pheromone collar. Separation anxiety is a wide subject that has to be understood in a proper manner. The major reason of separation anxiety is that the inflicted doggie is been left alone or is not getting the adequate amount of attention from you, the pet owner. Now as you have mentioned in your question, your daughter and wife, or any one of them, pays a lot of attention to the younger English bulldog then the oldie bull doggie gets all yappy and snappy. Which is inevitable, so you can’t do much about it. So, I am telling you one thing, which you should convey to other family members of yours. The first thing is, do not be biased while showering love and affection on either of the two pets. I can understand the simple fact that when the younger mini Aussie doggie was a pup, then you did not have any choice, but to impart proper attention to the doggie, but now as it is a grown up then you should be wary of the fact that imposing much attention on the younger one will offend the old English bulldog. So distribute love in an equal fashion.