Whiterun market-stall owners are occasionally overheard yelling at him; most notably Ysolda, who will sometimes refuse to give him money for alcohol.
If the Dragonborn is naked he will say, "Either I'm drunk or you're naked. Possibly both."
If the Dragonborn helps Brenuin and he dies, a courier will give a Letter of Inheritance for 100 septims (90 septims from the Jarl's tax) to the Dragonborn, which is quite a hefty sum for a beggar.
Despite being a Redguard, when Brenuin converses with Ysolda, he states that he is a Nord. This may be an inconsistency left over from changes and adaptations across the course of the game's development.
Brenuin appears to be homeless, and is never seen sleeping; instead, he wanders around the city or loiters in the marketplace.
According to Lucia, Brenuin is the only one in Whiterun who cares for her and he got Lucia into begging; however he offers no dialogue concerning her.