Reaction (spoilers)
1. The imposter is a selfish liar, and he must be a wicked sick person to be able to lie like he doesn't care about the reaction of a desperate family who lost her child.
2. The FBI agent is naive and incompetent.
3. I couldn't blame the family, they wanted their son back, they didn't care if he changed that much, they're obviously idiots who don't see the danger of the situation, but I can't blame them for more.
4. The private detective is the only sane and reasonable person in this story.
5. The brother who committed suicide knew something. Maybe he killed his brother, maybe not.
6. I'm not surprised he's father is algerian.