Complex sentence: Johnson told assembled students and alumni that having a chance to "come home and speak to my family" was the most special moment of his career, and defined his "family" in this context as the teachers that affected and changed his life.
Split into simpler sentences: Johnson told assembled students and alumni that having a chance to "come home and speak to my family," was the most special moment of his career. Johnson defined his "family" in this context as the teachers that affected and changed his life.