Who is Joseph from Z for Zachariah and what is their importance?

Joseph was Ann's brother. Joseph was a year older than Ann. Joseph went with his father to the Ogdentown to see if they could learn what happened to cause the phones to go out. When they arrived, they saw terrible things. Joseph cried when he came home, something Ann had never seen him do. When Ann's parents went again to investigate outside the valley, Joseph went with them.