Dain I was the son of Nain II, King of Durin’s Folk
He was the father to Thror, Gror and Fror, and brother to Borin. Born T.A 2440 he lived while Durin’s Folk lived in the Grey Mountains. He spent most of his life under his father King Nain’s rule and eventually became King of Durin’s Folk after his father’s death in T.A 2585.
Dain ruled for four years, during this period dragon attacks increased and a Cold-Drake killed Dain and his son Fror at the gate of his Halls.
After his death his eldest son Thror became King of Durin’s folk and relocated to the Lonely Mountain, while his other son Gror founded his own realm in the Iron Hills.