Nidge
it would be much worse if you could not warn your son, you did not choose for this to happen to you it just has, fate, sign of modern times, bad luck or call it what you will. There should be no blame associated at all.
Mick had a somewhat estranged son who was never really part of our everyday life (unlike his daughter who is my life) He was 40 shortly after Mick was diagnosed and we managed to track him down through my step daughter, I was worried he would somehow try to blame his Dad as he has for other things that have gone wrong in his life, but he did not. If anything it slghtly reconciled them. He got tested at 40 and everything so far is fine. He really appreciated being advised. It also taught me a huge lesson that estrangement doesn't mean that someone doesn't still care. He is no longer estranged he just keeps himself to himself! I think all directly related males have some right to know.
I don't make a thing of it to the men in my family or male friends as I feel that would be presumptious, in any case that is really a different scenario. I answer questions if they are asked. However I do try to make them aware of possible symptoms and of what they have the right to ask for if they are concerned by sharing posts of national campaigns and current publicity with them mostly via social media. That way it becomes informed by choice.
Best wishes to you
xx
Mo