But in case you don't, here are the FACTS.
Josh's mom was married to Cher's dad. They were married about five years prior to the start of the film.
That means at one point, Cher and Josh became stepsiblings.
But then between that time and the start of the movie, Josh's mom and Cher's dad got divorced, and thus Josh and Cher became ex-stepsiblings.
In the movie, Josh is visiting home from college and comes to help Cher's dad with some work.
Cher's dad mentions that he hasn't seen him since Easter.
Mel: Josh, are you still growing? You look taller than you did at Easter.
Josh: I don't think so.
Mel: Doesn't he look bigger?
Cher: His head does.