He is her first cousin once removed but I think you're supposed to refer to them as uncle/aunt yeah.
Fudge... Aside from harem, they also want incest as well? Dude, they're either her DIRECT cousin or Uncle!
I mean yeah i love this manga and the plot but duuudes whyyy?
Mmm yes and no? It's technically incest by our modern standards but this seems to be following the historical example of royals marrying as close as their first cousins to maintain pure bloodlines. This has been going on since royalty has existed in ancient times and has only started petering out in I believe the late 1800s/early 1900s. Considering the time frame of this manga it's really not that odd to see.
Wow... You're awesome! Btw, thanks for the info! You're a lifesaver, y'kno?
Blonde hair dude is her youngest uncle, dude with blue hair is her cousin, and the captain knight is the late king's nephew in simpler terms, the fl's dad is his cousin so kinda like an uncle