I have several questions that I am very concerned about. I have been worried for many months, and I really hope you can help me answer some of them.

My grandmother and both of her sisters have type 2 diabetes. My boyfriend who is now 28, has type 1 diabetes (diagnosed when he was four years old). What are the chances of our children having diabetes?
At the current moment, my boyfriend shows no signs of impotency. Do the chances of impotency increase as he gets older?
Do you have any statistical information about impotency and infertility in men who have type 1 diabetes? (For example: What percentage of men have infertility problems? What percentage have experienced impotence?)
Is the average life expectancy of a person with type 1 diabetes (diagnosed at age four) lower than the average person?

I will try and answer your questions as best I can. However, there is not enough information to answer all your questions.

The chance of your children having type 2 diabetes is not clear because I do not know if you have any first degree relatives with type 2 diabetes. If one of your parents or a sibling has type 2 diabetes, than you have a 40-50% chance of developing type 2 diabetes. If you have type 2 diabetes, than your children have a 40-50% chance of developing type 2 diabetes. The inheritance of type 1 diabetes is considerably lower with a slightly different rate of occurrence, depending on whether mom or dad has type 1 diabetes. In this case, dad has type 1 diabetes, and the rate of development of type 1 diabetes in his children is roughly 6%.
Impotence (also referred to as erectile dysfunction) occurs as a result of the nerves being involved with diabetes. The risk of this development is dependent on the cumulative exposure to high blood sugars. This means that the longer that a man has diabetes and the higher their sugars are during that time, the more likely they are to develop neuropathy and impotence. However, this does not necessarily result in loss of fertility. In fact, with newer medications, erectile impotence in patients with type 1 diabetes can be treated so that patients may have a meaningful and satisfactory sexual relationship with their partner.
There is data regarding longevity and the diagnosis of diabetes. Unfortunately, there is some data which suggests patients with both type 1 and type 2 diabetes have decreased longevity. However, I would suggest that better blood sugar control over time will improve quality and length of life. I would want you to concentrate on the possibilities of the latter through the practice of good diabetes care over a lifetime.

JTL