My dad died 21 years back. I still sometimes address him in present tense than past. Both my mom and brother are past it, but i still remember it. I dont grieve for him i.e. i dont cry for him or keep on thinking about him. But i know that there is a part of my life that is empty as he is not there. It does not help that he was essentially the only person in my life that i was at peace with. He also had traits like me and i did not have to work for my relationship with him at all.
I think i have held on to him longer than my family because they are not rigid by nature. They can change easily. For me it is not that way. There are things that i did with him and although i have tried doing those things recently, they are not fun as he is missing.
Actually i dont even get death in many ways. For me the person just exists somewhere i can reach, if it makes sense.
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Disclaimer: Not diagnosed but have traits.