Some people just really don't have any idea how to handle death and tend to just try to ignore it as much as possible. Not saying that is "right", but it can be the reality.

It is very doubtful though that they remember this is the anniversary of his death as he isn't their own relative. Thinking they would remember this a year later, particularly since they didn't really acknowledge his death when it happened might be a bit unrealistic.

Anger is part of grief. I lost my sister a bit over a year ago, and anger is part of what I go through. It may be your anger at them is really more about your grief for him. That's okay. That's just what we go through.