Who is Duno Brossler from A Thread of Grace and what is their importance?

The young son of Hermann and Frieda Brossler, Duno is from Austria. The Jewish Brosslers leave their aging grandmother, Rivka, behind, knowing she cannot make the journey over the mountains, and knowing she will be killed. During their trek through the Alps, Duno leaves his arguing parents and joins the resistance movement, becoming a partisan who hides in the mountains. He also leaves behind his two sisters, Liesl and Steffi. Having lived in the same hotel in Sant'Andrea when they were young, he and Claudia Blum are friends. Dr. Schramm teaches Duno about medicine and how to care for the injured. Duno is one who survives the war, and we can assume he goes on to be a doctor.