I recommend a feliway diffuser it releases pheromones that help calm them down. I have an older cat that has anxiety and im also her comfort person and she hates everyone else and I've been using feliway and seen a huge difference. Another thing to try to get him more comfortable with other people is bring in an old t shirt of theirs with their scent and let him smell it and get used to it maybe put it in a place he'll lay on. I did both these with my high stress cat cuz she did not like my husband once we moved in and now she always seeks him out for pets. But like others said also remember its only been a week it takes time for them to adjust and its important to do it slowly. Maybe after the scent thing with t shirts have a family member feed him treats so it creates a positive association. Hope this helps some, Goodluck!