HOW DOES HE KNOW 
My Top 5 Favorite Bl Manhwa
1 Passion
2 Codename Anastasia
4 Shutline
5 Payback
Bl:
https://mangabuddy.com/users/manga-list/152092
Action:
https://mangabuddy.com/users/manga-list/152096
Comment by AndIoop on The Rogue Prince Is Secretly an Omega - Chapter 60
1 Reply
@AndIoop it seems he found out when they were young