I'm trying to find a tv-series/mini-series that I viewed as a teenager, probably in the 90s, possibly late 80s.
A pair of siblings (twins as I remembers) grow up in a nice neighbourhood. One day an old lady moves in next door. Soon after, at a birthday the sister gets roller skates and is accidentally hit by a car. When taken to the hospital the doctors find that she doesn't seem to be human (not the right number of organs or something like that).
I can't remember the exact story after that, but it turns out that sister is actually an alien while the brother is a normal human. The neighbour is an alien as well sent to protect the girl. They are at some point attacked by light sabre wielding aliens (looking like big red bears on two legs and made of energy).
As I remember it ends with most of the family (at least the brother and sister) leaving the earth and as the sister leaves she turns into her alien form (lots of white shining light).
I don't think it is US made, possibly Canadian, Australian or from the UK.