I have an identical twin brother, who is also XXY.  We are vastly different.   He has many more health problems than I do.  However, he is not on testosterone.  He has above average bone density, mainly due to his job, since he works for a long distance carrier and is subject to weight bearing activities all day long.  I, on the other hand have a desk job, and my bone density showed 20% bone loss.  Our lifestyles are somewhat different, our educational backgrounds are different.  We were raised in the same home, and have identical genetic structures.  Our family history includes healthy parents at present, with minor health problems, not on any medications.  Our grandparents died of heart disease and colon cancer, well in their 80's.  Compared to my aunts and uncles, and cousins, I am alive and well at 45 yo.  A number of them have died, unfortunately at an early age from cancers, heart attacks, Down's syndrome, strokes, heart valve replacements, triple bypasses, liver disease, blood disorders, MVAs, homicides, suicides.   They had children, except for the Down's syndrome, but they all died under the age of 40.  I say this again, we are all individuals.  Just because you have health problems and an extra-X, does not mean that the rest of us that have an extra-X, also has the same problems.   Or will develop the same problems.  It is important that you let us know that you have problems, and also happen to be XXY.  In my case, my extended family history is much more complicated than my XXY history.  Genetics is a complicated science, not easily understood, and not always predicted.

Ron