What is this movie? Two kids, mother dies, jumping onto moving trains?

I think the mother is sick, bedridden. She calls one of her kids into
the room and gives them a necklace? Something to do with their father.
Then the mother dies while the kid is in the room. They have a funeral
scene, and the people the kids were stuck with were like nuns or
something. The kids runaway and jump onto a moving train, and on the
train they meet a guy who they talk to for a while. They go to a diner
or bar or something and eat...that's all I remember.