GrumpyCanadian I have no ideas on this case… its super tragic - there’s just no words. In my mind I can only see it going one of three ways in my random speculation –
1 - they really did just wander off in the woods and got tragically lost and with how dense the forest is, how many lakes and rivers and swamps are in the area, and how remote and rugged that area is, they may never be found or may be found in the late fall/winter/spring when there’s no foliage and visibility in the woods is better…
2 - they were walking along the road and someone random grabbed them - not very likely - the world has been looking for these two and their faces are plastered everywhere - it would be hard for someone to have the two kids and no one anywhere had any signings, leads, or information that led to them - its hard to hide 2 kids for months when you didn’t have them before - not impossible - but less probable… and finally…
3 - someone in the extended family is involved - they’ve essentially ruled out the step father - he’s taken every polygraph, interview, interrogation, etc with aplomb, there are no holes or gaps in his story, no inconsistencies, he’s shared his cell phone and its location history, his bank accounts, asked police to search anything and everything related to him, and there’s no sign he knew or did anything untoward and zero evidence of foul play in the household – but there is a lot of extended family and others who knew them who may have thought they were unsuitable or something as parents and have absconded with the kids - I think that’s what these further investigations and interviews are trying to look at - could someone in the wider community/family/circle have known or been involved and this was something planned and carried out with meticulous consideration. Birth father’s family? Mother’s family? Others who knew them well? I don’t have any guesses but I’m sure every one of them is being looked into until they reach dead ends.