How old were the members of kiss when it started?

The original members of Kiss were Paul Stanley (born January 20, 1952), Gene Simmons (born August 25, 1949), Ace Frehley (born April 27, 1951), and Peter Criss (born December 20, 1945). So when the band started in 1973, Stanley was 21, Simmons was 24, Frehley was 22, and Criss was 28.