That has been a longtime suspicion by many of the public, although it's not said out loud for fear of offending people.
The way they went about disrupting the police investigation, and jetting off to see the Pope (at whose expense!?), it seemed unreal.
Firstly, they should not have left the children alone to go off to eat- who does that at home, let alone in a foreign country??)
Secondly, they should have realised that everybody is questioned in this sort of investigation, why should the parents be ruled out?
Thirdly, how could anyone know that the children were left alone to begin with? Was the 'abducter' an opportunist who just happened to see her sleeping, or was it someone who knew they were neglected?