Grór was the younger son of King Dáin I, and younger brother of Frór and Thrór. When Thrór left the Iron Hills to reclaim the Kingdom of Erebor, Grór remained behind, ruling over the majority of Durin's folk even if his brother was King. The murder of Thror resulted in the climatic Battle of Azanulbizar in the year 2799. It is very likely that Gror had learned of the death of his brother, although his age may have been a factor that kept him from participating in the war, as his death was in 2805, five years later.

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