Are the twins from The Shining really twins?

Question

I recently watched again The Shining and I noticed something that confused me. At the begining of the movie, the guy who hires Jack Torrance says:

My predecessor in this job hired a man named Charles Grady as the winter caretaker. He came up with his wife and two little girls of about 8 and 10.

But then during the movie we see that those little girls were actually identical twins. I've look about if this is a plot mistake or it’s intentional but I cannot find much information, beyond "they are not because it is stated they are a different age" or "one is slightly taller than the other" (which seems surprising as the actress are actually twins, according to IMDb).

So is this a plot hole or was it intentional?

Answer 1

Yes they were twins but they wanted to cast two sisters only not twins, as sisters themself acknowledged:

“Stanley was the kind of person who didn’t know what he was looking for until he found it. We’d never been to stage school but we had done some TV work before and so we had an agent and she called our mum and said, ‘Stanley Kubrick is looking for sisters.’ Stanley was never looking for twins, but we went along anyway. If we hadn’t auditioned [then] the roles would probably have gone to two girls of different ages, like the characters in the book. It certainly worked in our favor because Stanley decided twins were just spookier.” - dreadcentral