As Tatiana Schlossberg underwent stem cell treatment for her terminal cancer battle, her siblings leapt into action to help. "My sister had turned out to be a match and would donate her stem cells," Tatiana, 35, wrote in a New Yorker essay published Saturday, November 22, referring to older sister Rose Schlossberg. "My brother [Jack Schlossberg] was a half-match, but he still asked every doctor if maybe a half-match was better, just in case." The Schlossberg siblings are the three children of Caroline Kennedy - the daughter of the late John F.