Who is Max Vandenburg from The Book Thief and what is their importance?

Max Vandenburg is 23-year-old Jew who hides from the Nazis in the Hubermanns' basement. He is a fighter who is fiercely proud and protective of the people he loves. He carries great guilt about putting the Hubermann's in danger. Both Max and Liesel feel like orphans. They share their dreams and nightmares with each other.