First off, I’m not familiar with the characters you’re talking about, so I can’t speak to specifics. But..

I’m gonna go ahead and give you my theory here.

I think that the people who insist that non-incest relationship are somehow “incest coded” have never experienced an actual nurturing relationship outside of their family before.

I think they’re stuck in cishet “MY WIIIFE” mode where a relationship is always two people who get together because they find each other sexually desirable and want to have children together and that’s it.

I don’t think they understand nurturing as romantic love.

I don’t think they understand the romantic attraction of actually being the one who cares for and uplifts your partner.