I concur with Nonini and Paa_Paw. Your genetics are going to determine most of your physical attributes. We have no problem accepting that you look like your parents; we also have illness and disease that are genetically based. Most gynecomastia is idiopathic, that is the medical term for “of unknown origin”. A biology professor in college liked to joke that it meant, “You were an idiot because you couldn’t figure out the cause.” His other line was, “You are on an idiot’s path trying to find the cause.” Everyone in the class remembered what idiopathic meant after that.