There are many different synonyms for the term "companion group." Some of the most common alternatives include "accompanying ensemble," "mutual alliance," "collaborative cohort," and "joint companionship." Other options might include "collective partnership," "shared squad," "cooperative unit," or "team camaraderie." Each of these terms describes a particular kind of social or professional relationship, but all share the basic idea of people or entities coming together in order to work towards a common goal or purpose. Whether you're looking for a more formal or informal way to describe a group of people working together, there are plenty of synonyms to choose from.