Based on Batman: Zero Year, Joker and Riddler are around the same age as Batman. But I'd say in the New 52, Joker is a bit older than Batman, so in his late 30s, and Riddler is a bit younger, in his early thirties. However, for Pre-52, Joker and Riddler both seem quite a bit older than Batman, and Harvey Dent is around the same age.
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Based on Batman: Zero Year, Joker and Riddler are around the same age as Batman. But I'd say in the New 52, Joker is a bit older than Batman, so in his late 30s, and Riddler is a bit younger, in his early thirties. However, for Pre-52, Joker and Riddler both seem quite a bit older than Batman, and Harvey Dent is around the same age.