If you follow the
Super DC Calendar 1976 which lists birthdays for most of the DCU's heroes, villains, and supporting cast, you note that, very imporobabky, no two characters' birthdays fall on the same day, with the exception of Superman and Captain Marvel (which fall on February 29, the most
unlikely day)!
However, here's a post-'76 aversion. Born today in 1966:
two heroes on the same day! At least, in the Post-Crisis but pre-Rebirth DCU: they're twins Jenny-Lynn Hayden and Todd Rice:
Jade and
Obsidian! As the children of the original Green Lantern Alan Scott, however, it's probable they no longer exist in the
Post-Rebirth (2016+) age, as Alan has been retconned to be a a gay man. Still, whatever retcon, you can never keep a good character down: even
Supergirl came back!
from Infinity Inc. (1984 series) #5 (DC, August 1984), text by Roy Thomas (?)
So remember: you have to buy two presents today, and you can't even get them the
same present: one has to be green; the other one has to be black. May I suggest color-coded
cardigans?
from Infinity Inc. (1984 series) #6 (DC, September 1984), text by Roy Thomas (?)
Happy birthday, you two wacky, possibly non-existent, certain weren't born in 1966 anyway kids!