
Ok first of all if their eyes are jewel-like only because of their second genders, why doesn't etienne's mother, a dominant omega, have jewel eyes? The answer is that only members of the IMPERIAL family who are alpha and omega have the jewel eyes.
Also, if he was adpoted by the king why is he considered a distant relative of the royal family instead of a direct member? Multiple people (including etienne's aunt) have pulled rank and told him not to challenge a direct member of the royal family. And which chapter does it say he was adopted? All I remember is that the King took him in after his father died. It seems more like the king took in a distant relative from eckhart family (who was related to him) rather than adopting a random kid off the street.

In one of the chapters it was mentioned that alphas and omegas have jewel eyes. Also the queen s red eyes have a sheen but you cant particularly see it fully bcs her eyes are redd and its already a very strong colour. Also he can be called a distant relative bcs some ducal families were given imperial last names to continue the bloodline in case the main didnt continue,but they arent always necessarily related. Though if they are I think its the fathers of each that are distant cousins which is fucking weird but I guess how that worked before and you would be right,but I still think it could be a mistranslation tho....
Honestly I wish they kept the novel design where Rishiar did not have the same colored eyes as etienne because every time they have sex I'm constantly reminded they are related.