Iìm looking for a yaoi with a prince,king or something like that have guys like concubin...

http://www.mangago.zone/read-manga/rakuda_tsukai_to_ouji_no_yoru/ (Story 2)

http://www.mangago.zone/read-manga/black_sun/an/black-sun-chapter-1.html/

These are the only ones I knew that are close enough. I'm sure there are entire lists of these.

just a oneshot but it's still good. http://www.mangago.zone/read-manga/harem/

http://www.mangago.zone/read-manga/tsuki_to_yabanjin/

I have my own collection. just check my notes, I've put the pairings there http://www.mangago.zone/people/tag/49344/royalty%2Fnobility/

also, black sun mc is about generals not nobles. (the uke served as a slave the whole duration of the story so it should not count)

Thanks guys :-)