Does this movie exist?

I remember as a kid I watched a movie, I don't remember much about it
but it was about some kind of man/monster who kidnapped a bunch of
children and then took 1 in particular and at the end of the movie the
dad is at the cemetery or wherever thinking about his son and he sees
his son but now his son is also a monster like the man.

If you could help me that would be great! :)