Renée wasn't supposed to be born a tiefling. (Though, it's really only the Chelaxians that hold that sort of tradition.) Being so obviously oni blooded didn't really help his social standing, despite his family's money and reputation.
The Seville family has been a staple in the Jade Quarter for generations. If you see a large shop of fancy curiosities or an overtly opulent tavern it's pretty likely to be owned by a Seville. Renée's own parents were purveyors of fine foreign alcoholic beverages of which they often traveled the world to collect. They didn't tend to bring Renée with him, so he was often left with his half brother Pierre and his step sister Sherry to run the shop. Renée tended to spend all of his time in the back keeping himself as hidden away from customers as possible. His face, as his step sister very often reminded him, was bad for business.
Despite the naming convention of the Seville family, there very little Taldan blood amongst them. Their family hails from Minkai where Renée's great grandfather Míng Lo Xìng was already a pretty terrifying entrepreneurial force. His ties with the Yakuza gave him a very steady source of power and income, and why he left Minkai to live in Kalsgard is quite the mystery to everyone but his family. Lo Xìng was absolutely fascinated by Taldan culture, Galt in particular. This fascination ran so deep that as soon as he moved to Kalsgard he changed his name to Arnaude Seville and set up a Galt inspired inn called Le Rai d'Or (The Ray of Gold). This inn has become a very successful staple of the Seville family and in its most decadent suite resides the secret to how the Seville line attained the fortune that it has. The very much still alive Arnaude Seville, who is also very much a Kuwa Oni.
Arnaude's secret is known only to himself. To the outside world Arnaude's family line is nearly cursed. When the oldest son stands to inherit the inn his father always disappears or dies. However, this is only half true. In order to lessen suspicions about his real identity Arnaude when he grows too old he kills the next in line and shapechanges into him, taking on his life and thus inheriting his own estate. One can only image Arnaude's disdain when one of his great grandchildren/nephews was born with a distinctly oni-like appearance.
Renée spent his life well cared for. He was always put in the finest clothes, given the best foods, and locked in the nicest ivory towers. His mother died giving birth to him, and it was his father, the newest Arnaude, who protected him so fiercely. However, when Renée's father inherited Le Rai d'Or he suddenly grew cold towards Renée and started looking for any excuse to disinherit him and cast him out to the wolves. It was Pierre that often protected him from their father's sudden ire, finding it strange that the kind-hearted man would change so much so quickly. Sherry, who blamed the man for her own mother's death, felt that it was really only a matter of time before he showed his true colors to the world.
The reason for why Renée went from pampered and protected aristocrat to homeless brawler is a common one. Renée had always found himself talented at violence, and his appearance aided his intimidation. Since he was of little use to the family in the shop, Pierre would often send him out to collect debts with Sherry. Sherry was meant to sweet talk people into giving them what they were owed, but more often she resorted to having Renée break bones instead. Pierre didn't really catch wind of this for some time, and was appalled when he learned about it. Not because he was opposed to forceful collections of debts, but because it was Renée that was being used to do it.
While Renée himself was never particularly prone to violence, Pierre often acted as though he were always one step away from turning into a monster. Sherry was usually trying to get him to indulge in what she assumed to be his basic nature, and the debt collecting was just another attempt in a long line of them since they were children. In truth Renée was as sweet natured as their father had once been, and while his sibling's assumptions did bother him, he would usually just quietly agree with whomever he was with, not wanting to lose his only friends by putting up a fuss.
When their father found out about Sherry's forceful, sometimes deadly, means of collecting debts it was Renée who shouldered all of the blame. This was the final reason needed to cast him out of the estate, which prompted objections from Pierre, but not Sherry who didn't want to be punished in kind.
Renée left the Jade Quarter and began making his way southward. He found adventuring to be a good way of making money and friends, as those sorts tended to like having a monster that could hit things well running along with them. However, the ones that were most comfortable with him were also quite dubious in nature, and the ones who matched his nature assumed him to be dubious. His run ins with Aasimars have ended particularly violently due to this. It was usually clerics and others of the divine that manage to judge him accurately, but that is when they bother to use magic to aid them.
This didn't mean Renée never made real friends, but being adventurers caused them to always had to part ways. His longest running friendship was with a Varisian Bladed Scarf Dancer named Zanzibar. He was vibrant and cunning and managed to peg Renée as a good soul from the start. They wandered around for quite some time, picking up and dropping party members along the way. Zanzibar was from Korvosa and as he felt he was reaching the end of his traveling career the two of them were going to open up a tavern there to call home. Things went decently well at first, but then some traveling merchants came in and bought the building the two of them had been breaking their backs to save up for. Zanzibar, deeply angered by this, went to confront them. Demanding that they give back what he felt they had stolen. The merchants scoffed at him and sent him on his way, but Zanzibar wasn't deterred. He was clever, and he wanted that building, so he took to investigating the merchants for blackmail. What he discovered got him killed, and Renée thrown into a torture dungeon.