what is "the heart of it all"?

[alicepmint]

No: HPFGUIDX 77487

I always thought it has something to do with "shipping/relationships 
theories", since she said it under the context of being asked about 
fan's unlikely pairings theories.

Quote from article
=============================================
JEREMY PAXMAN: Unlikely pairings? Not Hermione and Draco Malfoy or 
anything like that? 

JK ROWLING: I don't really want to say as it will ruin all the fan 
sites. They have such fun with their theories ... and it is fun, it 
is fun. And some of them even get quite close. No-one has ever - I 
have gone and looked at some of it and no-one's ever ... There is one 
thing that if anyone guessed I would be really annoyed as it is kind 
of the heart of it all. And it kind of explains everything and no-
one's quite got there but a couple of people have skirted it. So you 
know, I would be pretty miffed after thirteen or fourteen years of 
writing the books if someone just came along and said I think this 
will happen in book seven. Because it is too late, I couldn't divert 
now, everything has been building up to it, and I've laid all my 
clues. 
=============================================

My take? It has something to do with Lily and the men related to her 
(including Voldemort). 
Or Harry & Neville, since their counter-part qualities and 
similiaries were "built up" since Book 1.

Alice