Panda Bros: Twin Cubs Were Fraternal Brothers, Tests Show

Twin pandas born at the Smithsonian's National Zoo would have been fraternal brothers, if the firstborn cub hadn't died just five days after making its debut on Earth. Tests on the pandas' DNA showed that both cubs were male, according to researchers at the Smithsonian Conservation Biology Institute's (SCBI) Center for Conservation and Evolutionary Genetics. Furthermore, a paternity analysis showed that Tian Tian (t-YEN t-YEN) fathered the twins, the zoo said.