Ask them if they could sit down to talk to you about something deep and personal, yes, they will ask what's going on, but from that point start doing breathing exercises because you will begin to get nervous. If and when they ask if you're okay, simply tell them you need a little time to catch your breath.
After you have completed that, slowly come out with it but at your own pace. They will understand once you've told them what's needed to be said.
i had to sit my mother down and tell her i was pansexual. she didn't take it too well, but i told her something she told me from the past and that was she would always accept me for who i was no matter what.
my father...it took me longer to tell him.
you just sit them down, tell them you want to be respected for your choice, and no matter what they should love you because you're you
i would, just tell them if they love you then they will accept you no matter what you are and if they dont accept you then you really just have to give them time its hard for parents to hear those kind of things from there child just be aware of the reactions you may get.
Look at the situation, well most parents are always ready to have a talk with their kids, just to make sure that they are not having something important to be done. next: you can take William's advice :) Good luck