Pretty sure Ran isn't adopted, she's just extra baggage from the second wife's side. She only got entered in to the registry just because. Sharing the same household and ended up together is the few least weird union compare to a lot other shenanigans in the noble's case. Besides, public opinion can be won over or even ignored from their houses' perspective. As long as it doesn't break the imperial law.
Haha. If you're iffy about couples that share the same last name beforehand, I can only imagine with the case of cousins and close incest related themes.
I was a lil worried about that as well, but with how nonchalantly the uncle was like “haha yes, marry your cousin!”, I’m starting to think that it could be way worse then non related siblings getting married! (≧∀≦)
I'm always worried about making a romance between adoptive siblings when their sibling relationship is so public. It's the publicity of it that bothers me, you can say that they don't feel about each other like siblings, But society still views them as such, I just worry about the social impacts of them marrying each other and having children when they're literally viewed as siblings by society. Lol, this one and Beware of the Brothers bother me in this regard.