I'm from Australia and not UK and I'm a little surprised at the UK coverage of the whole event. There seems to be an overwhelming bias (especially with Sky News), where they defend and divert all the attention from the real issue. When they became suspects, people started discussing the "past" of the officer in charge and "offers" being made for them to confess, but in reality offering lesser terms of sentences for admitting to a crime is common - that's a fact. There seems to be a strong case for factual evidence against the parents and people are too busy defending them because they've grown accustomed to them and embraced them and their cause. This isn't aimed at everyone but, for those who defend them regardless of the outcome, you must remember you don't really know them at all. Anyone is capable and it'd be a shame if the facts of the case weren't accepted by the masses.
The whole they did it/they didn't is speculative at best, but once you introduce DNA evidence I think it's a strong case.