I admit that from reading the summary I was very trepidatious about clicking on this story. Pedo isn't something I enjoy reading, and I avoid it as best I can. I understand you want to keep that air of mystery about your piece to some degree; I'm just letting you know that the immediate thought isn't that this story involves adults.
Moving along, I do like the perspective you show of Dean's thoughts, not only of the night that their mother died, but as life progressed. It goes a long way to rationalizing Dean's actions.
One thing I don't understand is why he goes from calling Sam "Little One" to "Baby" again, especially since that's also how he refers to his car.
Overall, I did find this much more interesting than I first thought it would be.
Happy writing.