Sci Fi movie about water shortages and a family living on a desert, the donkey dies delivering liquor to miners and is replaced by a robot, recent movie

Hey,

There’s this movie I watch when I was a little kid and its driving me crazy.  All that I can remember is that there was a brother and sister (I think they where staying at their aunts house or something) who meet this boy.  There is several scenes with them in the woods, I think they stole flowers from somebody lawn at one point and I think that at one point they run away and spend one night in a church not sure about that though.  In the end the boy (not the brother) ends up falling out of a tree and breaking his back (he dies).  I really hope someone else knows what this is.  Thank you! 🙂

So I remember watching this movie where the premise was that the main characters each had superpowers and they would all die when they were quite young. They took drugs to help this and as they came closer to dying they would take more and this is what would eventually kill them. As I said in the title the powers kept growing as the characters age and they are killed off by a central organisation that helped raise them so that the guy in charge would be the only one who was powerful. I think the organisation was also a school/orphanage and that this was where one of the final scenes took place which was a battle between the head of the organisation and the main characters, one of whom had gone rogue by stopping to take the medication that they were given.

Thanks for the help guys. This has been irritating me for ages.