Is Jet (new dog) a male or female pup? I believe a lot of times
a male/female mix generally works out better, than male/male.
Not always, but generaly speaking. I had a almost 3yr old male dog
& adopted a 4 mo old female pup who has a quite different
personality than the older dog. They get along great. It has
actually brought out the puppy in the older, shyer dog. I wish
you the best of luck.