Snipped and BBM for focus
I like your points on them being a very stable family with a very stable routine. This is what makes me think that, it wasn't them as much as maybe, what they saw or at one point walked in on.
I'll use what happened to me as an example. A while back I went to use the restroom, on the way to the restroom, in the hallway I saw a situation taking place... I was startled, and I walked away, and they watched me walk away. The honest thing for me to do is report what I witnessed. I did.
I cannot begin to explain the harassing, the dirty looks, the hateful remarks, on and on and on.
I don't think there is anything illegal or sinister with any three of these people in that home. But I've said it before and I'll say it again, I think one of them or more than one of them was at the wrong place at the wrong time and saw something they should never saw or witness something they should have never witnessed.