Really sorry to hear about your situation.

It's a difficult and very personal decision about telling you children things like this. When my wife was diagnosed we told our kids about the cancer and the type. We did not tell them the expected outcome nor timescales - they didn't ask directly if they had I think we'd have told them. They were 22 and 21 and the end 17 and 18 at diagnosis.

Not everybody feels able to be open about their illnesses even to their closest familly but if I were you I'd talk to him directly and calmly and tell him what you've told us how while you respect his right to privacy not knowing is distressing you so badly and that even if it is bad news you'd rather know.

That is always presuming that this is true

Bear in mind too that he may not know nor want to know the full extent and prognosis of his condition - he may be afraid that if he tells you you'll go running to Dr. Google or worse friends at the hospital and find out his life expectancy or something like that so you'd need to make him comfortable in trusting you.

For some people talking about it makes it real - denial can be a powerful self-protection tool - my wife always said she'd make a very good ostrich! I'm sure he loves you very much and doesn't want to let you see him in emotional pain and may not trust himself to tell you about it without breaking down.

Any none or or all of these may be at play here - you just have to be gentle with him, be supportive and hope that he gets to trust you enough to tell you - you may find that happens on impulse sometime when you least expect it.

He'll tell you when he's ready - of course he may never be ready but hard as it may be you're just going to have to accept that it's his body and his privacy - I'm sure they tell you stuff like that as a student nurse I'm afraid its no different when it's your dad