Are people with klinefelters syndrome still able to procreate?

Usually Infertile: True klinefelter's patients are usually infertile, but some have a reduced to severely reduced fertility. In those individuals, advanced reproductive assistance may help. Some "klinefelter" patients are diagnosed solely on appearance, when in fact, they are not true klinefelter's. Their fertility may not be affected. If there is any doubt, check it out.

Unlikely: As the process progresses with age the structures that create sperm will begin to fail. Natural offspring will not be possible, but they could arrange for assisted reproduction the same as any other infertile male.