He is the younger brother of Ksenia Essair (nee Warwicke), thus his mother is Naevia Warwicke. Or was.
He left Dalmasca, and House Warwicke, a long time ago. For a reason, probably right before Ksenia returned home the second time, so he has no idea Naevia is dead (but he won't care).
A younger son of House Warwicke, Visarion, formerly Visarion Warwicke, was born about ten or so years after his eldest sister, Ksenia. He is, at present, the youngest of the Warwicke line, at least his generation, but most don't remember him, now. As he was a son, he was raised with all the Dalmascan patriarchy expectations of that, including that he was someday going to take over as lead of House Warwicke.
Unlike the other noble houses, however, Warwicke don't generally care who leads the House, as long as someone does. It was mostly expected that Ksenia take the lead, but their mother Naevia found an excuse to ship her off to another House, Kenleigh was first, which was their patron house at the time. Visarion never terribly liked House Kenleigh's leader, but he kept his counsel. It was probably for the best. Some year or so later, Ksenia came back, and Naevia had a panic, withdrawing House Warwicke's support of Kenleigh, and putting the house instead behind House Essair.
House Essair was... a bit better, but only marginally. Vopiscus was a right piece of work, and Visarion never did much care for him. He did, inevitably, get into rather the argument with Naevia over her decisions to essentially pawn Ksenia off on any house that wanted her in a bid to get their family useful blood relations. It ended terribly, as these things often do, and Visarion stormed out of the house to go think somewhere by himself.
He'd intended to eventually go back, mind you. Somehow, it just got lost, somewhere in there. In the end, he got himself a horse, and went west. House Warwicke had lost its mind, maybe Dalmasca had never had a mind to lose, and by then, Visarion was quite well sick of... everything. His travels took him in something of a circle, he actually got very close to the Kharga Desert, in the Valley of Nashret, but eventually he went back north, and came to the gates of Haradi.
No idea what he intended to do there, but perhaps he could learn a craft of some kind, and live out his days as a normal, regular craftsman. Well as luck would have it, he ended up in a spar with a member of the Haradian Crownsguard; they were bored, he was bored, hey, why not, and they recommended he join the Crownsguard. House Assad were rulers Visarion could certainly get behind, so he joined.
And somehow ended up leading it.
Now, if you asked him how, he'll tell you he has no earthly idea, because he doesn't. Okay, no idea. All the same, he finds he doesn't terribly mind this outcome. Of course, about five or six years ago, Prince Tihaan went missing. Visarion was the first to suggest slavers, as he had seen them within the walls many times before, and would not at all be surprised to learn they had something to do with it. What was surprising was that Dalmasca hadn't, apparently, decided to play underhandedly and trap House Assad by holding one of theirs hostage. No, it seemed Dalmasca had no idea who, exactly, they'd caught in their slave trade lines, but Visarion wasn't about to inform them of this. Instead, some time after Prince Ryhil left, Visarion and a few of the other Crownsguard left Haradi, and travelled to Dalmasca in search of the missing prince.
They made friends, along the way. Visarion is both fortunate and cursed, as he knows enough about Dalmasca to get himself and his people around without trouble, but then the thought occurred to him that brothel slaves hear a lot of gossip. It was possible they may hear of Tihaan, and he eventually got to frequenting brothels, rather high-dollar ones because rich men, above all, love hearing their own voice the most. He became good friends with a slave called Axelius, and his friend Pantheras, and the two were rather important contacts.
He lost Axelius about a year ago. Now, come to find, Pantheras is gone, too. Helene at least has a name for that one...