I saw parts of this film in the mid 90's. It was some kind of thriller of these two kids (brother & sister) who's parents had been murdered in their home. The son doesn't speak, and the police can't find out who killed the parents.

There was this weird scene where it's night time and the son is lying in the parents room where they were murdered and then the sister wakes up looking for him and finds him in there and lies with him.

Does any one know the name to this movie??

Almost sounds like (Michael Meyers in) the movie Halloween. I only watched it once.. so not totally positive.

It might be one of the Amityville Horror sequels. I know in one of them, there's a weird incestuous relationship.

I'll give this a try:

Silent Fall (1994)
Starring Richad Dreyfuss, Liv Tyler, Ben Faulkner
Wikipedia synopsis:
Tim, a boy with autism, has supposedly witnessed his parents' double murder. Jake, a former child psychiatrist turned therapist, is called on to probe the child's mind in order to solve the case.
The psychological drama is provided by the fact that not even Jake can entice Tim to communicate what he has or has not seen regarding the crime. Tim's sister, Sylvie, is protective of him. She eventually warms to Jake's efforts but is concerned when she learns he was implicated in the suicide of another young child who was under his care.

Silent Fall - Wikipedia, the free encyclopedia

Here's the movie trailer:
Silent Fall - YouTube