Important: this comment is a general one and not directed specifically at this post.
I understand what your saying and don't necessarily disagree. However, this guy isn't an experienced missing person expert and probably hasn't hired a PR team. He's a regular guy who just found out his brother and sister are missing, he has a new step-dad and his Mom is suspected of murdering a whole slew of people. That's a lot. He's also a millennial, which means a lot of his life has probably played out on social media. Self-videos are now so common many use them the way diaries were used years ago.
Yes it would be helpful if he gave us details of what the kids like, where they might be, etc. But imagine you're him going online to try to learn more about what's going on and see a comment some stranger made saying your video was frustrating and valueless. You would have thought it was impossible to feel even worse and yet now you do.
We look at these cases clinically so it's easy to forget our comments may be read by family members and friends--people w/raw emotions who may even be on the brink of despair. I urge everyone to remember this and make an effort to be kind while still making our point.
Perhaps something like this:
"I appreciate the brother making this video. It's obvious he's going through a horrible shock, loves his siblings very much and is concerned about their safety. I hope he does another video soon giving information on what the kids like, the kind of places they may be found, etc. so we can help find them. I'm also curious what he thinks about his mother. Maybe he'll be willing to share that as well."
In this case there are more affected friends/family than we can shake a stick at, and it's going to get a whole lot worse for them before it gets better.
Something to consider anyway. IRL I'm not preachy-critical-bleeding-heart-Girl. I'm really not. But I've seen the emotional toil some likely well-intentioned remarks took on SW friends and family and I see comments differently now. This just happened to be the post I was reading when the thought struck.
@SuperTmo, you're posts on this case have been wonderful and I hope you don't take my comment personally.