Matryoshka Principle
When you're going out with some girl and come to find out her family has between 3-5 other similarly looking/shaped females of varying ages/height that you also want to be shagging.
BOY 1: "Dude, my new girl has a younger AND older sister that look just like her but even hotter! And her mom ain't too shabby, either."
BOY 2: "Yeah? That MILF I'm banging on the slide has three daughters that I'm planning to go all Matryoshka Principle on."
BOY 2: "Yeah? That MILF I'm banging on the slide has three daughters that I'm planning to go all Matryoshka Principle on."