I think he's male, but maybe because he's mixed, he got certain stuff from Gok's female lycan side. That is the ability of marking another the same way female lycans can.
Around that time, even until today, the tan guy (Seolhyun) thinks that he's male. So he assumed that after his adopted brother hugged him, he thought that his brother's smell was still lingering over his body making Hwa react to it back on chapter 66/67.
So he thinks that way because of a misunderstanding. Aside from that, there is also the fact that he got his memories erased or were manipulated into forgetting his actual gender.
It seems that many could not see my previous comment from last month where I did resume and explained the situation in season 2 (starts on chapter 66). Aside from some spoilers that I might/will have written. So here it goes:
- WHO IS WHO?
A: Seolhyun IS THE FEMALE Lycan (female+ ?).
Lee Hwa is a hybrid (female Lycan + vampire).
Seolhyun's adopted brother is NOT a female Lycan rather a male one because if it was, the elders wouldn't have sent Ino (the white-haired Lycan) to get Hwa Gok to make a purebred Lycan baby back in season 1.
- WHEN DID THEY MEET?
A: When they were children, they bonded and marked each other. However, something happened and both got their memories erased. But Seolhyun got his memories partially erased because he could still remember Lee, but not the other way around. Not only that, but he also is not aware that he is a female Lycan, thus explaining his guilty feelings in thinking that he's leading Lee regarding his gender.
- WHY DID THEY GET THEIR MEMORIES ERASED?
A: Well, the Lycans elders are all about keeping the blood pure and making some purebred wolves. So Seolhyun and Lee getting together spoil their plans since they did lose HwaGok in season 1 (again). That's why they went into extreme methods to keep Seolhyun under their noses (they did something to Seolhyun's parents, so I rather not spoil), placed him into Ino's family, manipulated and lied to him about his gender.
- WHAT NOW?
A: At the moment, we just got to see how they stay together, despite all the drama coming, e.g.: hateful old lycan guy, babies coming, danger, split personality, death threats, memory loss, well...... the usual. It will be a fun ride.
Anything, just anything please just ask, and I will do my best to explain.ヾ(❀╹◡╹)ﾉ~