In book 7:
We find out Harry, Hermione, and Tonks were all dosed with love potion and that's why they act so fucked up in HBP.
Voldemort is really a time travelling Ron, who goes crazy after Hermione, Ginny, Tonks, Hannah, Susan, Lavender, Parvati, Padma, Lisa Turpin, Su Li, Luna, Pansy, Tracey Davis, Narcissa, Bellatrix, Fleur, Gabrielle and Daphne Greengrass all fall in love with Harry and Ron realizes he will die a virgin if he stays friends with Harry. I mean who would want a jealous, unmotivated, inconsiderate glutton like Ron when you could have the hero of the wizarding world?
JKR finally shows how Dumbledore is at fault for most of the terrible things that have happened in the last 50 years or so.