Responses
http://www.mangago.zone/read-manga/the_man_in_the_mirror/
http://www.mangago.zone/read-manga/emperor_stay_here_your_knight_s_getting_off_work/
maybe you could check out some tags?
I found this: http://www.mangago.zone/tag/royalty%20bl/ that has a lot of what you're looking for, you can also maybe use royalty yaoi or some other key words
Any recommendations for Royalty themed BLs? Something that maybe has 2 princes in love with each other?