I just straight up told my parents and they thought I was joking(they were anti-veg too). After about a week of staying with this new diet they started to notice that I was being serious. At first they tried to stop me by arguing all the usual arguments, but because all the refutes to those arguments can easily be found online I just looked them up for help.
Yes I was being made fun of and at times even be called foolish or dumb for doing so, but eventually they calmed down about it and eventually accepted my strange new diet(and they are kinda almost starting to support it, maybe).
for instance, just today I came back from work and my mom had bought me all these vitamins and supplements to make sure I was getting all the proper nutrients, and then she sat down with me to teach me how to eat vegetarian the right way. Most of this stuff I already knew but I could tell she actually did some research on her own to help me out.
Moral of the story is:
1. Be strong and stick with it. Remember there is strength in numbers and I'm sure the people in these forum far out number the number of people in your family. We'll back you up anyway we can.
2. Breaking the Ice is always the hardest part, you can either go loud or quiet but once you tell them you'll be glad you did and that its over.
3. You never know, maybe because of your decision someday your family and friends will look into this and do a little research of there own and decide to be vegetarian too!
Can't really think of anything else to say except, Welcome to Veggie Boards!!!
Edit: Sorry, somehow didn't notice that your already a vegetarian (this is my official blonde moment of the week). I'll leave my original post up because its like a great piece of art or something (it also might be useful for someone, somewhere).