I get where you are coming from. And I think plenty says he may be the suspect. But here is contrary evidence to that.
He was the first one questioned, and they questioned him a long time, then released him. Rumors on FB do say that he took and "passed" a polygraph. His truck, and the clothing inside was of extreme interest, early on. Since that time, they have focused on a different vehicle as well (maybe because they couldn't find anything after tearing his apart?)
He is described as having lived with CC as her brother, and my interpretation of what I read on FB is that he lived with CC and her family since his Dad and LN were involved. He may have only been living there "a little while" recently because he was in prison for awhile, and may have moved in recently when he got out.
He has no record of violent criminal behavior.
The Noyes family, OTOH has several known SO's. I think that history gets me more suspicious so far than KM's does. But, jmo. Either way, I think it's all a guess right now until we have more to go on.