I'm so sorry about this, Alffe.
I understand what it is like to be on the outside of your family although not by suicide. Your grandson was very young when Michael died, I was about ten when my Dad left me. I have no doubt that his fathers death was traumatic for him and sometimes the only way to deal with trauma is to suppress it. He had a lot of years growing up without this father so try not to be hurt because he won't acknowledge his Dad. It's normal but not necessarily healthy and it's probably just his way of dealing with the pain.
I'm so sorry that you can't share the memories of Michael with your grandson.
I hope I helped some... and I'm so sorry if I didn't.