Stormer: 13.10.
-Libra ♎

Bulk: 06.12.
-Sagittarius ♐

Stringer: 17.11.
-Scorpio ♏

Furno: 03.08.
-Leo ♌

Surge: 21.03.
-Pisces ♓

Breez: 29.05.
-Gemini ♊

Evo and Nex: 31.03.
-Aries ♈
-They were created on the same day (I think), so same birthdays

Rocka: 04.07.
-Cancer ♋

Zib: 29.02.
-Pisces ♓
-He would technically be 10 years old because of the leap year

Quadle: 11.01.
-Aquarius ♒

And before you ask, no, I chose the birthdays randomly, not because of the Zodiac signs. It's all random and I just looked up the signs for each birthday.