It is a real fear and we get it. I was the youngest of 10 children with a huge gap of 8 years to my nearest sibling. My Dad died of cancer just after my 1st son was born. I was truly devastated that somebody who I thought would be involved in my kids lives wasn't going to be. My Mum passed when my youngest was 8 of natural causes.
Nobody can predict what will happen and I get your sadness around it.
I have developed traditions that celebrate my parents in my family. The big pots of soup and hot bread like we had at home. The Xmas menu. Billy tea when camping. Lots of things that remind me of my Mum and Dad and my children have grown up talking about them and remembering stories about them (even my Dad who 2 never met). So lovely...if you are not there in person it doesn't mean your essence of who you are won't be. Write about yourself. Collect special recipes. Do all the things that will help your son bring your memory not only into his life forever but forward into his childrens. Kath x