I now know of two couples in which the members share the same birth date and year. The first: my friends Eugene and So-Young, who celebrate their tenth (!) anniversary this year, I believe.
The second: Christo and Jeanne-Claude — the back flap of this Gates book has a C/J-C timeline, and 1935 reads:
"Christo: American, Bulgarian born Christo Javacheff, June 13, Gabrovo, of an industrialist family. Studies at Fine Arts Academies in sofia and Vienna.
"Jeanne-Claude: American, French born Jeanne-Claude Denat de Guillebon, June 13, Casablanca, of a French military family, educated in France and Switzerland."