Ida,
You are who you are and no one can say otherwise. I would say family is important, as it should be...but at the same time if they cannot accept who you are, then who are they to decide what you wear and how you act. I know I am still in early pre stages. No hormones, no therapy, et etc.. but what I can advise is this.
If they truly understand who you are, they would accept you no matter what, and would have you over wearing whatever you wanted (though exempt on this is provocative or no clothes) and wouldn't give you trouble as such.
Approaching them and talking to them as who you are, in whatever clothes you feel comfortable in, plainly state that if they cannot meet you halfway at a pure minimum, you will have to break ties with them. If they cannot love you unconditionally, then they are pushing you further and further away.
I do not have experience with the unaccepting parents from being transgender, but I know when I met my significant other, and had eventually married, my mom was unaccepting, and despised her like crazy, my whole family was pretty neutral on the whole thing. But in the ways that I broke ties with my family back then, had moved to Georgia, to Southern California, had very limited contact, and very brief when it came to talking. Later on when my wife had said that I should talk with my family or at least call more often, so I did, and pretty much "bam" accepting.
My story is different than what you are trying to go for in the whole as acceptance for who you are and not who you are with. But what I am getting at is warn them that what they are doing is pushing you away, and if they keep persisting you will go away, they will realize eventually of their own mistakes, and slowly recuperate to want you back in their lives, but as you are and not as you used to be.
I hope I can help with this.
Let's all climb aboard the choo choo train to happiness
Kateā„