Heather Corinna replies:
How do I best support a family member who has come out to me? The person is 15 years old and says they are bisexual.
The next thing to do after a family member says that to you is simply to acknowledge what they have disclosed and honor that it can be scary to do that -- such as by saying something like, "I'm glad you felt safe telling me about your bisexuality."
You can also reassure them that until they're ready to come out to anyone else, you'll respect their privacy.
After that, you can ask if there's anything they need from you. Do they need to talk about it and have you listen? Do they need your support in coming out to other friends and family, or help figuring out if the time is right to do that? Do they need to be reassured you accept them? Do they want your help or company in finding additional support, information or community? If they're dating someone same-sex, do they want you to meet them?
If you have any questions, you can ask if it's alright if you ask them. What I'd just advise is that, if you're heterosexual, you consider the questions you'd ask as if they were being asked about your heterosexuality. If it seems like someone asking a similar question of you would be invasive, would just be something you can't possibly answer or which just isn't very sensible (such as "How do you know for sure you're bisexual?" or "Do you think this is a phase?"), then step back. Your family member may or may not be ready for or up to answering questions right away, and their need to disclose and talk about what they're ready to and want to should take precedence.
And that's really it: this is all about being a good listener, assuring your sibling, stepsibling, cousin or whoever else that you accept and love them just as they are, and being responsive to their needs. What a given person coming out wants and needs varies a lot. Some may just need to tell someone and have that telling be all they need for the time being. others may want help in feeling out if coming out to the rest of the family is safe. Others may want help getting more information or active support. So long as you make clear you're there for them and open to their needs -- and that you acknowledge their truth -- it's all good.
You say this person "says" they are bisexual, so I just want to make sure that you're hearing that the same way you would if someone said to you that they were heterosexual, or that they got a new job, or that they're moving down the street. In other words, if this person says to you that they are bisexual, this person is -- so far as they know, just like a person is straight as far as they know, or has that new job as far as they know -- bisexual. That's what I mean by acknowledging their truth.
Good on you for asking what the right thing to do is and being invested in supporting your family member. So many gay, lesbian and bisexual teens and adults don't get any family support, and many even face violence in coming out or being found out. Rest assured that if you earnestly want to be supportive, it's going to be pretty hard to screw up.
PFLAG has a nice guide for families of gays, lesbians and bisexuals which you might find useful here. Here are a few more links which may help you out: