I have a tiny bit of suspicion too about Kaine!! I'd like to know why Desiree filed a RO against him a few years ago!
People, in general, and I include myself in this, like for things to be black and white because it makes life easier to deal with, but real life is incredibly, horribly, frustratingly messy.
I think it's easier to paint Terri as a narcissist or say she is using steroids and snapped or any number of things as a way to explain what happened to this poor child, but what if Terri gained weight and Kaine tormented her about it or what if he was verbally, mentally, and/or physically abusive? Prior to this incident, there was certainly no love lost between Desiree and Kaine, and I think it's rather telling that she left him while she was pregnant and eventually filed an RO against him.
I personally don't think Kaine had anything to do with Kyron's disappearance, but that doesn't mean he's a good person, either.