If he displays this submissive posture to some of them, but not others, those are the ones who still need to work on their own alpha posture and methods. They should take him back through another tour of boot camp with support from the rest of the family. Once your dog has begun to accept this new way of life and his new position in the family, you should take him through an obedience course with a qualified trainer. It teaches you how to be alpha, how to enforce commands and rules, how to get respect and to keep it. All family members who are old enough to understand and control the dog should participate in the class.
Obedience training is a lifelong process.
Obedience commands need to be practiced and incorporated into your daily life. In a dog pack, the alpha animal uses occasional reminders to reinforce his authority. A well-trained obedient dog is a happy dog and a joy to live with. Dogs want to please and need a job to do. Training gives them the opportunity to do both.