Birthday Roll Call

There are two astrological signs missing from the Gaggle. Could it be that those for whom I don't know birthdays fit in the vacant categories?

Aries - Rob
Taurus - Jon
Gemini - Amy
Cancer - AJ
Leo - ???
Virgo - Peter
Libra - James
Scorpio - Gary
Sagittarius - ???
Capricorn - Sheridan
Aquarius - Dustin
Pisces - Thom