If I have 2 vampire aristocrat in play and I sacrifice a creature do both vampire aristocrats get the +2/+2?
If I have 2 vampire aristocrat in play and I sacrifice a creature do both vampire aristocrats get the +2/+2?
Each would require their own sacrifice to trigger the ability.
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Correction - the ability never triggers. It's not a triggered ability, it's an activated one (written in the form "cost: effect"). Each activation requires its own cost to be paid. A popular way of putting it is that you can't use one coin in two vending machines.
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