Difficult son

I would appreciate views on years of indifference from son and very rare telephone calls/emails and hardly any visits - he says we live too far away although we visit him and his family and stay in a hotel. the latest episode was to hang the phone up on me on Xmas day with the statement he had made the effort to call. He is a successful 37 year old with his own home a lovely wife and adorable grandson (1yr old). My daughter in law has told me there is a historical problem but won't tell what. Her parents have said the same. I have Parkinsons and feel that I just want to cut ties with him and stop trying (not with my daughter in law and grandson) - any advice would be helpful.