Not to be harsh but you say the dog seems like an intruder and you want it to act like your other dog. Whoa this is all you. You were not ready, but if the dog is great and your family is bonding you most likely will too. I just lost my best dog friend in January after almost 14 years together. Four months later I was ready and we purposefully got a dog very different from the first. Give it time. Stop calling it an intruder though

that would be a good start.