Responses
I think they maybe have some sort of twisted and depending relationship with each other, with a lot if guilt in it. I think, the parents died because of them. Or they think its their fault, whatever it is, it is about guilt, revenge and 'paying'.
...meaning that it could be (or is) a glimpse of things to come! And it all makes sense now, after chapter 24! So, if we take the prelude to be the absolute future (or truth, as the author is the one who's playing mind games with US, the readers), I think it's highly possible that every word and action taken by Law is premeditated and designed to confuse as well as manipulate Jesse into thinking and doing certain things! After all, in the prelude, Law says "...I created the present you." And, in the prelude, Jesse asks, "This is real, right?", just as he's doing in the present, when he becomes uncertain about what's real and what's false (right after he allegedly falls asleep after looking at Law's pictures).
But dammit, I really, sincerely hope it doesn't end with Jesse as the loser in this twisted play! He may not be a "good" person, but then again, no one in this world is. We all have our own faults (I, for one, am quite twistedly cynical). I want Law, as the one who's presumably had the upper hand for a very long time, to taste defeat, once and for all! Σ(っ°Д °;)っ