Bout this whole genetic thing… I know I am late but just wanted to share what I have heard:
You will not get an argument from me about people getting diabetes because Hashem wanted them to. Obviously, as believing Jews, we believe that. We also believe that people lose their job because Hashem wanted them to. Does that stop us from trying to find and keep a job? Of course not. As believing Jews, we believe that a person gets sick because Hashem wanted them to. DOes that stop us from seeking out the best doctors, spending any amount of money on medicine and treatment? Of course not.
Similarly, just because a person only gets diabetes because Hashem wants them to, doesnt mean we shouldn’t try our absolute best to prevent ourselves from getting it. With type 2, it’s simple. Try to eat right and exercise and you are doing your hishtadlus. With type one, its a lot harder. Doctors don’t know what causes type one diabetes, and so we don’t know what hishtadlus to prevent it is. We do, however, know that (and this is coming from doctors and rabbanim who know a lot more about the topic than any of us on this forum) when two people with type one diabetes have kids, the risk of the kids having type one diabetes are much higher than when only one (or no) parent has it.
That’s why the advice I got is not to date boys with type one diabetes, and that is why (I believe) Rabbi Meisels is against it in most cases. You can ask your own shayla, but in general, it is not reccomended.