Well, that sound tough... 😕 But if you're bigender boy and girl they can still believe there are only two genders - you're just both of them. 🤔 I mean, ideally they would also learn about other genders outside of the binary but the first step is accepting you for who you are so it's ok to start small. The first step might be figuring out if they believe gender to be tied to a person's sex or if they're ok with the concept of transgender (within the boundaries of the binary gender construct, so just mtf and ftm for a start). You might be able to introduce that topic through a movie or tv series with a transgender character or music by a transgender artist perhaps. Everything else will then depend on their reation.