I am so, so sorry. At nine years old, they should know what 'no' means. It's pretty simple. I would definitely, and diplomatically, have a talk again with your parents and let them know the conversation you had with your sibling. She deliberately did what she was told not to, knowing full well it would endanger the lives of the chicks. Chicks are cute but they are only for responsible people. I have 2 sons, 7 and 4, and they don't touch the chicks unless I say so. On your next go-round, leave the brooder in your room with your chicks and maybe set up a brooder for your siblings. When they cook their own, maybe they'll understand better. On the flip side, they may really admire your successes and want to be as successful as you've been. Maybe they are hoping some of your ample knowledge rubs of on them.
Look on here for Elite Silkies, she has some and may cut you a deal based on your bum luck. If she doesn't have any, she can probably tell you where you can get them.
Check also at Strombergs, you may not get eggs but they have the blue Silkies.
So here's a
to the ol' boyfriend, a
for you, and prayers for happy hatching (I just did my first batch). Never say never, it's very hard now, I know, and very sad too. Don't give up on your dream. If we gave up on dreams, we'd have nothing. Yup, it may take a while to get what you want again but good things will come.