Bereavement - not feeling sad?

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My grandfather passed away nearly two weeks ago. He was 91 and had had an active life until April this year, since when he was in and out of hospital. I was very close to both my grandparents (My Gran died in 2000), however I don't feel the same way about my grandfather's death as my granmother's (I cried for days). I was wondering if anyone could shed any light on this. I was 20 when my gran died and 29 now. Am I weird or has anyone else been through this.