FILE - In this Saturday, June 18, 2005 file photo, identical twins Alf, left, and Sven Fehnhanhn, left background, 79, from Kassel, pose along with seven-month-old Luis Carl, right, und Albert Frank Millgramm, right background, during a twins' meeting in Berlin. According to research published on Thursday, Jan. 7, 2021, identical twins are not exactly genetically the same. (AP Photo/Jockel Finck)