In your fiction what would count as good match ups? For example, in my stories, Eileen trains up a young fairy called Hanastrew, who develops into powerful fairy godmother in her own right and takes over Eileen's role in fighting evil when the latter defects to Earth. Eileen, prior to her defection, realises how talented Hanastrew is and, rather than resenting it, encourages it. She sees Hanastrew, correctly, as a good match for her.
So who would be a good match for your main characters? The great thing is they need not be friends. They can be someone unexpected but there should be a good reason why they are the match up to that character. Sometimes someone can reflect the virtues/faults of the main characters. Equally they can react against these things so the main character(s) could see how things might have gone for them had they chosen to take a different path in life.