I always thought of Shiva and Siren to be females, I think they are quite obvious in their genders. I have always thought of Carbuncle to be female

Ifrit, Brothers, Diablos, Cereberus, Alexander, Bahamut, Leviathan and Griever. Quezacotl, tonberry, Pandemona, and Cactuar I have always thought as male.

The only one I am undecided about is Eden. It's either a Garden, a male or female. I have no idea which.

About juctioning Squall always have to have Quezacotl.