Hello, I’m polyamorous. I have been for a very long time. I didn’t find out until a few years ago that it had a name. I have usually have dated a boy and girl at once. But I recently started dating another boy who is m2f trans but before the hormones. But since that is even a secret, our relationship also is so far. I wanted to know how I could tell people about it without it sounding like I want their approval. I just want them to know; friends and family.
When you date a trans person, especially someone who’s in the process of transitioning or coming out, it’s important that you let them take the lead in things like this - without getting yourself into a situation that’s unhealthy for you, of course. (I noticed that you referred to your new partner as a “boy,” even though they identify as female - I’d recommend that you talk with your partner about how they want you to think of and refer to them. If that’s already a conversation you’ve had, ignore this note.)
As for letting your family know - it can be very difficult and painful to keep a relationship secret, especially if it’s your partner who wants it to be secret. I would suggest you speak with your partner about the fact that they’re an important part of you life, and you’d like to share that with friends and family.
Maybe they are OK being introduced as your “boyfriend” for now, and you two together will navigate the coming out and transition together. Maybe they want to be introduced as your “girlfriend,” which might mean you will need to have some conversations with your friends and family about the fact that their perceptions and expectations don’t trump another person’s identity. Or maybe they really do need you to keep the relationship private for now - in which case, you can choose to honor that, or to leave the relationship if being unable to be open is a dealbreaker for you.