It doesn't have anything to do with family though. The same questions are being asked - who was the last person to see the victim? What were they doing? Where were they when they separated? What did the person who last saw the victim do afterwards? Where did they go? Did they have reason to hurt the person? Does that person have a criminal history? Does that person have a financial motive? - and so on.I think everyone is entitled to their own opinion, even if we disagree, we should be respectful. Just because someone thinks a family member is or isn’t involved, let them share their thoughts. Yes, I’ve said I think family is involved and I right now I still do. If it turns out I’m wrong, I’ll admit it.
In this case that person happens to be a family member by marriage, which apparently rubs some people the wrong way.
My opinion only.