Actors don't sinc-up with the ages of the characters
Shirley MacLaine does not look old enough to have been a middle aged woman with a grown daughter 40 years beforehand.
Kevin Costner does not look old enough to have been a college kid 39 years earlier.
Jennifer Aniston looks a lot older than the actress playing her younger sister-unless their mom died during that childbirth?
Oh, and Jennifer's character looked to nutsy to be conducting herself like that at 40 years old.
Shame they didn't do this movie 10 years earlier (29 year old woman and say a 25 year old younger sister, etc.)
With some recasting the story would have made more sense.