How to tell my parents I think I'm ? I'm a teen please help?!?

Okay well I know my mom and step dad will probably be supportive but my biological dad and his girlfriend are phobics and I'm scared to tell them. How should I bring it up? And btw idk if this has anything to do with it but I am anything but boyish... I'm very very very girly and live being a girl. Thanks so much!!!!:)