A few thoughts-
* Neither of the missing adults seem to have a job of substance, yet they seem to be doing alright. I wonder if either of them has at some stage inherited money, which is funding their reasonably sound lifestyle- nice house, nice area, overseas holidays. If there is some kind of family trust, would that be exempt from bankruptcy proceedings?
* NO was not meant to be there- I dont get a feeling that he is in any way a target here, just in the wrong place at the wrong time.
* What ever JO found in that house must have been pretty over the top to get the immediate attention of the police in such a way. There must, too, have been something that indicated the presence of someone else, otherwise why would domestic involvement be ruled out so quickly? Unless it wasnt ruled out, and just put out there to calm whoever was responsible down.