I have no grandparents left. I have lost two aunts and one uncle. I have lost my closest friends one by one save the one (my dogs). The only thing to equate to this experience, and it doesn't match in any way, are my two lost marriages. One day (figuratively) you have someone in your life, and then the next you don't.
I know it is no surprise to anyone that the first affected me far more than the second. If you know me personally, you know the story of my life, if you don't know me well, then you don't and probably won't. I digress. The difference is, that if you are both semi-mature people, you can still have a friendship of sorts, and still converse after the period of mourning has passed.
Death is different. Losing a parent is different.
I have often said that a ex-spouse is like a limb that when it is removed, you feel the loss and you will never be whole again. If you are, then you are not a true soulful person. You are no better than an animal. You cut something off that you had grafted in to your body, you should feel the loss forever. Should you mourn forever? No. But you should make your next life choices mindful that you affected another's life or were affected by another's life so deeply. Divorce is not a trivial matter. But it is not death.
Losing a parent is different.
It is like you are torn in two and the two sides cannot be put back together again. You cannot speak, think, or move without that parent being echoed in your voice, words, thoughts or mannerisms. You are the sum of your parents. Of course you have life experiences, other environments, people, etc., thrown in. Who would argue that you don't look like, sound like, talk like one or both of your parents? No matter how you try, you will hear your father or mother's words flowing from your mouth and roll your eyes at the very same things.
Losing a parent is losing half of yourself. The only thing that will rival this is losing the other parent, a sibling. They say losing a child is worse. I'll never know. I lost my hope of children a while ago, that in itself was a death, but I do deal with the mortality of it daily--as I age. Which makes the losing of my core family, just that much more painful.
I know I will move on. But for now, I need to feel this pain. I am 44 years old and haven't lost anyone I loved with all my heart and soul before. My dad never lied to me. He could gargle glass as far as I was concerned. He is gone forever.