I watched this film on TV, possibly around 2006-08. I can't recall if it used any CGI, but it seemed quite modern, as if it had been made in the 90s - early 2000s.
I think it was a fantasy film, but I can't remember the plot. All I'm sure of is there were two children, both with brown hair, possibly around 10/11, and I think the girl was older than the boy.
The only scene I can remember is one in which they're in some kind of underground dungeon or chamber, and realise that they can speak telepathically to each other- I think it's limited to/caused by the room, rather than being a super power they have.
I think I can remember some of the lines?
Girl "Hey, think something to me"
Then I think the boy said something and they laughed.