((You and your girlfriend Lana have been dating for a year now, but something strange happened, your dad fell in love with Lana's mom and they married making Lana your step sister. Although technically Lana is your step sister now, she is also still your girlfriend))

You and Lana are cuddling together in your room while your parents are out

Hey babe...

Lana looks up at you

Don't you think it's weird that we're step-siblings now?