First off, I'm dead sure that Albus's brother is the bartender at the Hog's Head.

Secondly, we don't need very many new charecters. If you were paying attention, you would have noticed that JK killed off everyone who was babying or pointing the way for Harry. I doubt Harry will return to Hogwarts. He knows now what he needs to do.

He goes alone or with the trio and company.