From Day 1 info has been withheld and distorted by the parents. Their very first story is simply not believable - we are out in the wilderness, with poor cell coverage and a 45 minute drive to civilization, but we're going to "explore" without our 2 year old who is probably the most curious to explore than any of them, and we're going to leave the 2 year old with his elderly great grandpa who is oxygen dependent and in "poor health", and oh, our campsite is just yards from a steep embankment at the bottom of which is a creek, and great grandpa couldn't possibly catch him if he took off in that direction. Oh, we also didn't make absolutely certain that grandpa knew he was in charge of the two year old, because what could go wrong in that scenario?
Responsible parents do not do that. When you're in a new place with a toddler you're hyper-vigilant.
You don't do interviews in which you lavish praise on the searchers who haven't actually found the kid yet. Yes, thanking them for their efforts is appropriate but not gushing on and on about how amazing they are. They can't be that amazing if the boy is still missing.
They actively rejected efforts to help them, including Vilt offering up $20K of his own money as a reward. Seriously?! Who turns down that kind of assistance? Oh, I know...someone who already knows where the child is, that's who.
They declined to talk to the media because they didn't want their words twisted - BS. They didn't want it to be so damn obvious that they couldn't keep their stories straight.
They let his eye color go uncorrected on the missing poster for MONTHS.
They have angrily reacted publicly to the accusations that they know more than they're saying, but the local law enforcement agency, the FBI, and two private investigators have come to the conclusion that they are lying.
None of their actions since he disappeared have been geared towards finding him, but many of their actions have been geared towards preventing him being found.
There's nothing about them that is NOT suspicious, in my opinion. I think even their loyal families have begun to doubt their innocence, despite their statements of total belief in them.