Quote Originally Posted by Cygnus View Post
As far as I know, whether you belong to a clan depends almost entirely upon your surname (there are exceptions - people with differing surnames who offer fealty to the chief, those who owed fealty based on their geographic location, etc.) - if you were officially adopted by a McLean, and your grandfather was officially adopted into a McLean family, then you are a McLean!
This is my take on it as well. Your last name is McLean, so you are member of the Clan McLean. Wear the McLean tartan with pride!