What is recommended to help to fix a class ii jaw line?

Class II mandible: Class ii indicates that the lower jaw is behind the upper jaw. It can be a skeletal or a dental problem. Yours sounds skeletal, since you refer to the jaw line. If the lower jaw is in fact too short, the only way to lengthen it is with surgery, which is very common. If it's just the chin that's too short, that can be addressed separately. You should see a trained oral and maxillofacial surgeon.