Their siblings relationship is still just that if you paid attention! Bro threw a blanket over Enisha when he was changing so she couldn’t see him which is normal sibling behaviour when your in the same room T-T. I do agree that was some poorly times fan service but when else would we get to see the twins than with their sister lol
They really manage to work in a plot twist into every single arc in this manga and they’re always so good, this has gotta be one of the best stories in the genre