My brother and I are also close and he is the one who got me to go to the seminar with him. We both planned to be banded and support each other. Then his job wouldn't let him take off and through a serious of unfortunate events, he has no idea when or if he'll be able to get the band.
When I shared my success with him I thought we were talking as partners, two people interested in the same thing. Instead of making him look forward to it or happy for me, he could only feel sad that he's trapped, for the moment in a body that he despises.
I vowed right then to myself never to mention it again. He tells me from time to time that he can tell I'm losing and he trys to support me but I never make him hear about my weight loss in any way.
Most people just can't be happy for you, even if they love you and want you to succeed. I've found that most just can't hear about it. My sister, who has always been the smallest is very supportive and will let me ramble on all day about how loose my pants are or what I had to eat that day. She's the only one I share that kind of information with. For everyone else, I only tell if they ask.
You need to find someone who can honestly hear about it and not have issues with it. Let your sister off the hook. She wants you to be happy, but it's only going to hurt her to have to hear about your weight.
If you can't find someone around you who you can share with, use this board or a support group as Aubrie suggested.
I know how hard it is not to shout this from the mountain tops. You just have to be careful of other people's feelings.
Having said that, Congrats on your weight loss and please come back and tell us when you have your next victory. I jumped on here to tell everyone I moved out of the plus sized department and got so much support here!
Best of luck to you.