Former President John F Kennedy’s only grandson Jack Schlossberg has vowed to leave social media “forever” after attacking his cousin RFK Jr., Megyn Kelly, Elon Musk, and more, in a flurry of incoherent posts that left some concerned about his mental health. “I’m sorry to everyone. I Was wrong. I’m deleting all my social media. Forever,” he wrote, before deleting his accounts. Schlossberg—whose mother Caroline Kennedy ripped first cousin RFK Jr. as a “predator” ahead of his confirmation hearing to be Health and Human Services secretary—faced backlash in January for seemingly mocking his cousin’s spasmodic dysphonia, a neurological disorder that...