DH's cousin died in a tragic road traffic accident when his cousin was a teenager, in a couple of months time it will be a big anniversary of his death. There will be a memorial service and get together afterwards which DH and myself will be attending. That side of DH's family live roughly 3 hours away from us. The issue is DS who is 20 and at uni has been invited but does not want to attend. The uni that DS is at is even further away from where we would be travelling to. For context the cousin died before DS was born. DH is worried that DS lack of attendance will not go unnoticed. AIBU to think it's not rude of DS not to attend?