He had an older brother, Thrór, and a younger brother, Grór. He was the second son of Dáin I. Frór spent his short life in the Grey Mountains. He was slain with his father when a Cold-drake invaded the doors of the mountain palace. Shortly after they were laid to rest in the tombs of the mountain halls, the kingship was passed on to Frór's older brother Thrór. Durin's Folk then resolved to abandon the Grey Mountains. It was Thrór who founded the kingdom of the Lonely Mountain and led a portion of his people there. However, the greater part of Durin's folk followed the youngest brother Grór to the Iron Hills.