A pair of abused siblings exact revenge against their parents in an attempt to find their long lost sister whom they believe is hidden somewhere in the family home – Precious Little Things

This idea may have been played out, but so what! Just about everything else has been and people will always go to the movies to see the same thing over and over. I think your Log Line is great, short and to the point. A filmmaker could take this idea in several different directions i.e. comedy or horror.

Simpsons did it

Good feedback, I'll consider your suggestions : )