I, naturally had two grandmothers - one for mom and one for dad.
One grandma lived the ultimate clean life, never drinking or smoking, working hard on their little farm, enjoying all good things in moderation and eating her own organic fruits and veggies. And she adored her husband of many decades and went to church on Sunday.
Other grandma was a bitter smoker who hated her husband (and most everyone else), drank vodka by the gallon, lied, cheated, played video poker and sat on her ass in her condo for decades, manipulating anyone who would be caught in her web.
Question: Which one lived past 90?
Trick Question! They both did - and are both still alive. Good Grandma is still good, Evil Grandma, well, she's out in Vegas somewhere and we don't keep in touch any more.
Moral of the story: It just don't matter.
It helps if you come from a long lived family too.