This is becoming a bit of a theme. This time it's his estranged half-brother. After assuming the identity of Don Draper, things are going well. He returns home, and eventually gets a job at Sterling Cooper, quickly climbing the ladder with his talents - he is even forgiven by the original Don's widow and starts a family. Soon though, his brother tracks him down. Unable to forget the time he saw his brother pass him on the train, Adam Whitman wants answers; he wants his brother back. Out of cowardice and embarrassment Don does his best to foist his brother off. Eventually he sends him $5000 dollars in a package and tells him never to show his face again. Naturally his brother is distraught. He really loved his Don; he wanted to re-establish ties with him, not blackmail him. Instead he's written off as a hustler. Some time after, he hangs himself. Don could never have known his actions would lead to his brother's death, and the extent to which he is responsible is debatable, but he is still haunted by guilt, hallucinating about his brother towards the end of Season 5.
