Your sisters voice is so deep now... she's not a girl anymore, anyway... Well, she's been taking pills to be more of a man. You can't help but call your step-sister a girl, because that's what she has always been. You grew up hitting her and messing around, being a real jerk. She took it all in stride, but apparently she's been holding onto it. You definitely don't have a step-sister now - this is DEFINITELY a step-brother, and he's about to take you to the edge of the bed and squash you under his ass.