Everett Michaels – Considering Brent's adventuring and such, he'd be injured quite a lot, so I could imagine that he'd be going to require Everett's services a lot. Don't know how much Everett would appreciate Brent's crazy personality though. Seeing how he's a health nut though, maybe Brent could have worked for him a few times in the past, searching for herbs and such? Brent might also be a bit pushy when it comes to Everett not exercising enough and building manly muscles. Oh yeah. Soup bros. Nuff said.
Alex Garnet – EXTREMELY interested. More specifically, Brent would have never seen someone like Alex before, and his previous research would have told him that she may be someone with both the souls of a male and a female. Which would make her an object of research. I don't know how she'd react to him, but chances are, he'd try to talk to her as much as possible. Lots of questions about her opinions and views as well. At the same time...it won't exactly be a true 'friendship', or even a friendly acquaintance. Perhaps we could develop something along that line?
Gaku Yamamoto – Brent would respect Gaku's bluntness and honesty. Seeing how he's an Inn worker, maybe they have some sort of...music-discussing relationship? Brent doesn't particularly like Rock, unless it has nice lyrics, and he could probably be introduced to Classical music via Gaku. He'd obviously dislike Gaku's own laziness though. Something along the lines of “If you're not going to work, can I have your job?”.
Eli Stern – Most likely, he'll think of her as his junior, as well as a rival to compete for jobs with. Perhaps something along the lines of...half-mentor half-competitor? I could imagine him contacting her whenever there's a job that two can do, if only because it's more fun to work in a team than alone. Other than that...perhaps they originally became acquainted when she went off to Fiora Falls to paint, and saw him bathing? XD
Isis Thorne – He'd find her a bit boring, considering how she enjoys 'calmer' things. So Brent and Isis would probably be more distant from other than the others. Not to mention that she likes hot springs to destress, while he likes cold showers to achieve Zen. Maybe they'd meet at the bar a few times though? Exchange a few stories when he's not busy 'chatting' with Alex? Would she have been one of the first people to greet/acquaint herself with him when Brent first came to Lily Town though?
Izzie McKenzie – Brent really likes her. Considering their personality, and the nature of Brent's own research, she'd probably tag along a lot. Like, gosh, I'd be hardpressed to find a reason that they wouldn't get alone (maybe that's just me being unimaginative though). Perhaps he'd have met her grandfather first though, considering he camps out in Fiora Falls? Probably be asking her grandpa a lot about the Goddess and the Spirits and the Witch as well.
Henry Manteel – Seeing how they were both originally from elite families, maybe they would have met in the past? Elementary school? It'd probably be onesided, with Henry hearing about Brent though. Outside that...Brent may have visited Henry a few times, just to say 'hi' and buy some super-fresh vegetables, but that'd be it. Think they might have set up an exchange system of sorts, in which farm-grown veggies are exchanged for wild, foraged vegetables?