It's official I guess.
Whenever a Tadano, Komi and Katai end up in the same room together it's instantaneously a mini mixed harem.
The difference being that the brother charms his counterparts both unwittingly and unknowingly while his sister, well, she kind of savagely forces them whether they want to or not.
They may try to resist, but their attempts are futile.
She scares me.