The only person we have evidence of being with the children at the time of their deaths is LVD & AC. MG stated JJ was w/AC when he was carrying the "sleeping child" and LVD was supposed to have JJ sleep in her room on the bed on the floor for JJ. We have the pics of JJ & Tylee w/LVD & AC @ YNP. I think there is a ton of forensic evidence on JJ's remains that will concretely prove it was LVD & AC w/JJ.
Tylee's death may be harder to prove who actually committed the murder. The condition in which the remains were found remind me of a case from a decade ago about a little girl (Zahra Baker) who's evil step mother chopped her up in bits and distributed her remains all over. That child had suffered from cancer and was missing a leg, her Mom was in Australia IIRC). It was so tragic. I don't think they could ever prove her Father was involved. My point is that there are females that are capable of horrific crimes like murder and dismemberment of children.
link to Zahra's story for those interested
Zahra Baker MEDIA links only **NO DISCUSSION**