As an infant, Tai and his twin brother were taken in by pirates. In fact, the crew had found the babies in a locked treasure chest, a very mysterious place to find newborns, definitely. The pirate crew taught them everything they know now about survival. Stealing, lying, trickery; all tools in their belt from a very young age. They were raised to believe that the whole world was theirs, if only they wished to take it for themselves.

Early life in Mondstadt

When the twins were around 8 years old, they found themselves trapped in Mondstadt during a particularly cold winter storm. The crew was late picking them up from their exploration due to the weather, and they ended up collapsing outside of the Dawn Winery. Upon seeing the state of the two young children, the master of the house, Crepus, took them inside and warmed them up. Inside, they met a fiery fourteen year old named Diluc, and a michevious twelve year old named Kaeya. The four of them bonded rather quickly, Diluc the obvious leader of the rag-tag group of children.

They spent many days and weeks and months under the care of Crepus. He taught them civil manners as well as the ins and outs of basic hygiene, gardening, and cleaning. They appreciated all the lessons, dutifully listening in exchange for a stable place to find food and shelter. Crepus treated them kingly, like they were his own children.

At twelve, however, the boys were with their crew when it was attacked by monsters at sea. Most of the crew was slaughtered, the rest sent adrift in the waves. As Tai was about to drown, he wished with all his might that he could only save his brother, and in the next moment, his vision appeared. Little did he know, Rai had wished for the same thing, and recieved his vision at the same moment. With their new visions, they managed to sweep themselves to shore. Although the ship was unsalvagable.

After this, they spent more and more time at the Dawn Winery. Tai liked to trail after Kaeya's every move like a little lost puppy, doing whatever he asked and begging him to play at all hours of the day.

Crepus's death and subsequent events

Unfortunately for them, this peace wouldn't last long. In Tai's fourteenth year, the twins had started travelling more and at longer distances. However, one day they came home to find that their adoptive father had been killed, Diluc was nowhere to be found, and Kaeya was holed up in Mondstadt, leaving the winery unattended. They scrambled to make arrangments for the winery, even going as far as attempting to make it seem as if Diluc never left, as to make sure no malicious entrepreneurs tried to lay claim to the business in it's masters absence.

Eventually they descended upon Mondstadt to find Kaeya, and found it was rather easy, as he was the cavalry captain now. However, when they met up with him, they noticed that he was not the jovial youth they knew before they left. In just a few months he went from warm to frigid cold. He wouldn't give them any information about Crepus's demise, and was even more closed off about Diluc's disappearance. Even going as far as to say "if he wishes to vanish, then that is his business, not mine." It was clear that something happened, but they were not privy to any of it.

Since Tai was only fourteen at the time, the shock of loosing more family sent him into a rage, which quickly spiraled down into depression. Rai suggested they leave Mondstadt for a while. And 'for a while' ended up being four years.

Return to Mondstadt

At eighteen, the two returned to Mondstadt. They'd grown significantly, in personality and height. Towering over even the tallest civilians at 6'2". Tai has developed into quite the trickster in the time that they were gone. He was known through the lands as a serial heartbreaker, infamous for chasing both blue haired beauties as well as any willing cryo user. He clearly had a type, but no one seemed to point it out to him, and he himself was none the wiser.

The Dawn Winery had thrived in their absence due to their proper long term planning. Tai was angered to see that Diluc still hadn't returned, even though inside it looked like no one had ever left, not a speck of dust to be scene. The cleaning crew were meticulous as always. They took up leadership positions at the winery once again, acting as Masters of the house in the heirs absense. As much as Tai wanted to find Kaeya and flaunt his growth spurt at him, Rai suggested he reel it in and focus on the important matters for long, however his resolve could only hold out for so long.

Eventually, Tai broke and went to search out his prey, the unassuming cavalry captain. It was harder to find him this time, but he eventually spotted him in the corner of a bar. It was as if he hadn't aged a day, still as devastatingly handsome and cold as the day he left.

In comparison, Tai was several feet taller, even taller than Kaeya now, with blazing red hair, and a more revealing manner of dress than he ever dared have as a youth. He walked leisurly up to Kaeya, seeing he was already fairly wasted, decided to tease him. Kaeya didn't seem to recognize him at first, and even accidentally slipped up and called him Diluc. To which, Tai froze. It was the first time he'd heard Kaeya mention Diluc since the incident four years ago, so he decided to play along. Kaeya's drunken state had loosened his tongue, and he let slip the true reason he and Diluc had gone their separate ways. That Kaeya had finally come clean about his past and Diluc had been enraged. But when Tai asked more about said past, Kaeya seemed to withdraw again, as if realizing he'd said something wrong, even in his inebriated state.

Tai helped him back to his appartment he apparently started living in, inside Mondstadt, but when he turned to leave, Kaeya gripped his sleeve, and even though he didn't say it out loud, his eyes screamed 'stay'. Tai softened, and nodded, coming inside and the two fell asleep curled up on Kaeya's bed.

The next morning, Tai woke early and ran to get breakfast, coming back to a severely hungover Kaeya. But once he entered the home, Kaeya froze, as if he thought that Tai had been some figment of his drunken imagination. He became closed off once again, and Tai wasn't even sure if Kaeya remembered what happened last night at all. He decided that if Kaeya was going to be a stone wall, they he might as well be coy in return, and heavily implied that they had slept together last night to tease him. When Kaeya looked sufficiantly horrified, Tai left him with a goodwill farewell, but once he was outside, his heart felt weird, as if it were broken.

He returned to the winery, only to see that Rai had already decided to go out for the week, if the note on his desk was anything to go by. And he found himself alone, once again.