ok well here is my opinion... and I talk too much and regularly offend people so I am really sorry in advance....
But I have suspected the parents since day 1, if I lost my LO I would not be thinking of media, or Popes or websites, I would be wailing and screaming and grieving, I would not be putting little green ribbons in my hair and strolling on the beach.
I would be hoarse from screaming and crying, not giving interviews.
But hey that's me.
Theories:
The parents sedated the kids so they could go out, and accidentally overdosed and killed her.
Madeleine caught Kate and the other male suspect in a clinch.... and well something.