Grouse was born in 2247, and he has been with the slavers since he was a teenager (he is now 30). His father was the former leader before Eulogy usurped him and rose to power, and Grouse has a legacy to live up to. He isn't fond of Eulogy, but he knows that if he moves against him, most of the slavers would turn on him. He sits at the checkpoint entrance wearing a permanent scowl.
Grouse is the only source of slave collars in the game. Should Grouse die the player will be unable to obtain a new slave collar or caps for a successful enslavement. However, so long as the player has a slave collar in inventory they will be able to use it to enslave a mezzed non-player character, albeit for no reward other than negative Karma (and removing the enslaved non-player character from the game).
He will become hostile if the player preaches to him for the second time after he dismisses the player. This will cause the rest of the slavers in Paradise Falls to become hostile as well.