The title meaning and Noel's history

The brother Jake mentions that the flies should all be long dead by then when he swats one on his neck, brother Noel says "well some hang on longer than others", but it's more likely just a metaphor for death and the rotting flesh on the island as they were shown a few times I suppose.

I don't think Noel was anywhere near as violent in his past or he wouldn't have lasted on the island for his entire life without any criminal charges.

If anything his brother Jake's arrival should have grounded him to some extent in a normal relationship, but since we found out that it was in fact Jake who shot and killed his father on purpose to defend Noel, not a hunting accident in which Noel was the responsible triggerman. Though Noel took the blame for his father's death and watched his mother kill herself so brother Jake arriving may have been the catalyst for the escalation of Noel's violence. It's obvious that he was and still is deeply troubled by those events, taking all the pictures down and ending contact with his brother for many years, as Jake said he barely has any memories of Noel. It's like Noel was never able to move past what happened with his parents and he just tried to bury it in his head, block it out and when his brother came it all surfaced making him into a crazy psychopath

I think it's safe to say, if Jake hadn't arrived there would be a lot less dead people around in the end.