Sorry about that. I'm thinking that I should give you the heads up since I'm afraid you'll get betrayed later.
But from my point, I've been shipping them from the start. Just hear me.....
My reason is, they don't feel like siblings at all. True, Anissa kept on calling Dietrich oppa, but that just because she wanted to get on his good side. Meanwhile Dietrich didn't even try to like Anissa, much more to see her as the little sister. But Anissa warming up to him. Their interactions is more like two strangers that shared the same circumstances. And the only reason Dietrich keep on calling her his little sister in front of people is because that's the only thing that give reason for him to protect her in front of the others.
And it seems both are aware they are not related.
It's not like something like....
"I love you brother/sister">>"what?! We're not related?">> And bam! "I think I love you romantically" .....
kind of plot

Or any of the other brothers pls just let them be a beautiful family