It's not ethically wrong, and I think it's very honorable that you've considered their feelings and are genuinely afraid of hurting them.
It may hurt them to see you this way, maybe they don't understand or they simply aren't used to it, or are used to seeing you as male, but it's not wrong to do what you are doing.
It's NEVER wrong to be yourself. Have you tried talking to them? Even if they don't understand, don't stop what you're doing. They may never understand how you feel, but don't let that get you down. It's really important that you do what makes you happy.
I hope this helped.