Umurn is the son of Chief Burguk and Gharol, one of his wives. She was given the job of Forge-Wife, thus having to provide weapons and armor for the stronghold. She has adopted him as an apprentice, and they both work outside of the mine.
According to dialogue, he hopes to one day forge a weapon suitable for a chief, perhaps himself. He has a full-blood sister named Lash gra-Dushnikh who has run away from the stronghold to the village of Karthwasten.
Should the Dragonborn kill any of the women within Dushnikh Yal, Umurn will hire two thugs to retaliate. A contract can be looted from the thugs which explains that the Dragonborn killed his "beloved." Umurn's thugs will appear even if he was previously killed.
Gharol: "Imagine the heads of your enemies as you forge. Let your hatred work the steel."
Umurn: "Yes, mother."
Umurn: "The metal has been stubborn today. It refuses to bend."
Gharol: "Save your anger for the forge. The steel cannot hear your whining."
Umurn: "Sorry, mother. I'll focus on my work."
Gharol: "Ah, is there any weapon finer than an Orc blade?"
Umurn: "No, mother. It's no wonder our enemies fear the sight of an Orc warrior."