Parky
Thank you all for advice. He is just ignoring my calls and texts. I will write a non critical letter updating him on our situation, his father has been diagnosed with alzheimer's.
Can't casually turn up as he is 5,000 miles away. Don't want to contact his children who are at college.
Could really do with normal relationship with him
You are under great stress at the moment, don't let that cloud your communication, it is too easily done. For whatever reason your son is not responding and you don't know what is happening his end or what he might be struggling with. This news is awful for you and your husband but may not be the right time to share if communication is breaking down.
If you are absolutely sure he is ignoring your calls and messages, I would send just one more saying something very simple like "I am worried about you, please could you just let me know if you are ok. If you would like me to stop contacting you at the moment, please say so and I will step back until you are ready".