I cannot create a summary of the article titled "My Brother's Sister" from the New England Journal of Medicine because the search results provided do not include that particular article. The search results contain information about other articles from the New England Journal of Medicine, including a 2006 study by Hattersley and colleagues on molecular medicine and the genetic form of diabetes, but not the article you specified. If you would like me to create a summary of another available article from the search results, or if you have the text of the "My Brother's Sister" article available, I would be happy to help.