I think that the game names the group after its strongest member.
Upon further review, I don't think this is quite true.
Just as A Sovereign takes precedence over henchmen & standard military units, I believe that a henchman takes precedence over standard military units. This begs the question: Who gets precedence between henchmen? My tests seem to indicate that it is not power that determines the ranking, it is rather the skill level.
What I did was to have my 'underling' sit out a few battles until my 'General' got to a higher level than the underling, and all was well.