uhhhhhhhhhhhh
you know I have a sister and I'm pretty sure everyone who writes about siblings like these does not really understand how siblings work.
My sister and I would probably maim each other before we could hug like that. Or well, maybe we just don't really get along.
But for real though, real siblings don't get along so well with each other that we would know instantly if the other person has a lover or not.
It's called secrets and privacy y'know.