Beginning/Ending? I'm confused!

just finished this movie..i liked the beginning and the ending was the same. however, the entire movie had nothing to do with it from what i gather. it was more violence/gore than i wanted to see but it intrigued me when they where going to explain the girl at the beginning. obviously, i'm an idiot so can someone please tell me WHO those 2 people where at the beginning. the girl during the movie (blonde) was 3 yrs old when this all happened to her. the girl at the beginning of the movie was not. she saw something and i never got what she saw. the acting was actually very good from the limited amount i could barely watch during violent scenes.