I think Shiro and Sora from No Game, No Life is an understatedly weird relationship, considering that they are siblings. (or step-siblings? I don't know anymore.) Sure they aren't really dating in the anime. I heard from a friend of a friend that apparently something like that happens in the manga, but I might've been getting trolled. I also believe they have some official "content" between the two of them out there. All that being said, even in the anime Shiro, definitely seems to fish for praise on her physical appearance from him.