@Mpazi it's okay... he doesn't want him to meet his brother is probably because how in the past taeju always remembered Dowon since Dowon confessed to taeju first and taeju rejected it. Also Dowon confessed to taeju Infront of everyone in the school and that's also the reason taeju always remember Dowon's name. And since his top is younger than him and wasn't even on the same grade with taeju unlike Dowon, on top of that he was too shy to interact with taeju back then, so taeju always remembered him as Dowon's little brother. Which you can see understandable since he didn't had much presense. And now that he finally got taeju his toxic jealousy is coming out as he's the overly obsessive type. Even though taeju and Dowon had no romantic interaction between them ever and Dowon has also someone he loves now, despite all these facts he doesn't want taeju to meet up with Dowon. From a normal point of view it's just because of his toxic jealousy nothing else