So I'm a bit confused about something. It might be a spoiler, so consider that your warning.
Lots of people mention Mikoto's letter to the Hoshidan royal children when Corrin gets an S Support with them as the way we find out they aren't actually related. It's a revelation, a secret finally revealed, and that's how it's treated.
...Except for one thing. In Corrin and Hinoka's B Support, Hinoka says Mikoto tried to talk her out of being a Sky Knight, referring to her as "your mother", as if it were common knowledge that Mikoto is only Corrin's mother. Corrin then says "Oh, she was worried even though you weren't related?", reaffirming the common knowledge point.
My question is: was that mentioned at some point in the Birthright story? I don't remember it, yet they treat it as if it were already known.
Why'd Nintendo call the Hoshidan siblings your brothers and sisters by blood in the advertising, and then just so casually mention the fact that that isn't true in that support?