In the years before his death, Osama bin Laden seemed to be grooming a successor to lead Al Qaeda: his own son. Here’s what we learned this week about those plans. Guest: Rukmini Callimachi, who covers terrorism for The New York Times. For more information on today’s episode, visit nytimes.com/thedaily.  Background reading: The care Osama bin Laden showed his son was not just fatherly, but appears to have been an attempt by the world’s most hunted terrorist to secure his legacy.The United States had a role in the operation that killed Hamza bin Laden, officials said. But other details, including where he died, are unknown.