i just had to draw something from BOTW and i accidentally fell in love with the optimistic fish prince
but in all seriousness take a headcanon
sidon mentions in-game that when hyrule fell 100 years ago, he was still a child (as they’re talking about mipha’s relationship with link)
so consider this: mipha babysitting a tiny little sidon (who, let’s be honest, would’ve been a huge bundle of joy). she was probably the one who taught him to be nice to everyone (hence the constant motivational speeches).
i feel like here he’s probably just reflecting on what he still remembers of his sister.