I mean, neither of them are a good choice for the character. Veronique is a smart redhead who's good with all sorts of creatures in the comics. She's mostly the calm and diplomatic one who can talk her way out of a situation and is usually in a good mood. Casting her with a blond person that has a resting bitch face throughout the movie is the worst offence to the character. Valerian is always portrayed as a bit hotheaded and lazy but also very smart and experienced. In the movie they made him some type of hotheaded action hero when him being experienced, techsavvy and a good strategist is a big part of his character in the comics.

That being said, the sibling thing isn't too far off. They are never portrayed as having a romantic relationship and (spoiler)