No one could predict when the disease would take his life, but without a transplant, it inevitably would. He carried it everywhere in a black and gray backpack. When he stopped gaining weight, a surgeon implanted a port in his chest that hooked to a nutrition bag. After he started school, they almost never showed up on time because one of the 14 different medications he took made him throw up in the morning. At age 4, he couldn’t take a step without leg braces and a walker. Her brother didn’t complain much about the extraordinarily rare disease, known as IPEX syndrome, that was ravaging his body, but she saw what it did to him. Seldom did he get a gift from a hospital charity without asking if his sister could have one, too. Reign never sensed Messiah was jealous of the things she could do that his illness deprived him of, and she never resented all the attention he received because of it. At night, in the darkness, they shared secrets, confiding their school crushes in each other. They made dozens of silly videos together for their pretend YouTube channel, the “Reign and Messiah Show.” It featured tumbles off their dad’s faux-leather chair and offbeat renditions of “Can’t Stop the Feeling!,” grainy tours of the bathroom and giggly shots of their parents, Toka and Will Howard, snoring. She helped teach him numbers and letters and the rules to “Guess Who,” which she usually won, unless he got frustrated and she eased up. She played with his Marvel figurines when he asked her to, pretending to be Captain America so he could be Black Panther. It was only possible because of Reign, who had doted on her little brother all his life. That day would be, as their family called it, Messiah’s “rebirth.” So, on that January afternoon, two weeks before the first American would be diagnosed with the novel coronavirus, the Howards and their doctor started discussing a date for the transplant, eventually settling on March 24. She had watched her brother suffer for years with a debilitating genetic disease and would do anything to help him feel better. She could say no if the surgery was too scary, the doctor at Children’s Hospital in New Orleans told her, but Reign didn’t hesitate. “Will it hurt?” she asked, and he told her that it would, at least for a few days. Messiah’s doctor tried to explain it to her as she sat in his office, her hair tied up in Afro puffs and her leopard-print sneakers dangling off the chair. Reign Howard knew that her brother, Messiah, 7, needed something called a bone marrow transplant, but she didn’t really understand what that meant. The first-grader was going to die if his doctors couldn’t find someone willing to save him, but nearly a year had passed since the search began, and now there was only one person left to ask: his 9-year-old sister.