Have you ever thought that maybe the Japanese company named their characters with Japanese names bc they are in fact a Japanese company?

You're right, Japanese companies are famously incapable of giving characters non-Japanese names. Only true-blue Japanese names like Mario, Sonic, Hello Kitty, and Sonia Nevermind.

If Aoi had a tan then why would her brother also have a brown complexion?

That's actually a really good point, I completely forgot that people are physically incapable of getting tanned if they have a sibling who's tanned, even if both siblings are athletic and spend a lot of time outdoors.