As a member of the blockbuster access pass (in-store) I'm renting more movies than I catch up with anymore. There was one I rented a while back that I didn't catch the end of but was planning on renting it again, problem is I forgot the name of it. Couldn't be any older than 3 or 4 years old.
It was about a young brother (around

and sister (around 17) who were at an orphanage waiting on adoptive parents. A married couple came in to adopt the young brother but he didn't want to go without his sister, so they adopted them both. The woman had a kid before but he got sick and died. She poisoned the young brother so she could "care" for him in some twisted way, while the older sister slowly started picking up clues about what was really going on. Her brother was dying but nobody was listening to her.
Didn't get any further than that but I imagine the older sister will save the day somehow.
Seems like a drama or some movie that'd come on the lifetime channel. Any ideas what it might have been?