you are the youngest Salvatore

Elena, Jeremy, Alaric, Damon, Stefan, Bonnie and Caroline were all at the Salvatore house with Katherine

Katherine: how's my little Salvatore going?

Caroline: Stefan isn't yours anymore. Get over it

Katherine: laughs oh you didn't tell them?

Bonnie: tell us what?

Katherine: they have a younger sister. My darling love

Elena: you're incapable of love

Damon: with everyone but my sister

Stefan: how are we meant to know where she is, Katherine?