Found - But denied

Hi all - This is my first post here. I am thinking that only people who have been through this process will understand. I have been searching for my birth family for 25 years. I had all the standard non-identifying info. I always knew I had an older brother, but apart from knowing my mother is 5'2" and 100 lbs, I had pretty much nothing else to go on. Letters sent in the 80s went unresponded to. I had decided that it wasn't meant to be and let it go. When my adoptive mom passed away, I felt if was right to start looking again. I mean - technology is so different, who knows? I reached back out to the agency, but found it was no longer in existence. A new agency had taken the files. I contacted them, and this time received much more information, apparently they thought that so long as they didn't give me last names, it was fine. So I received my mother's first and middle name, the first names of my grandparents, an uncle and my brother. I also received the first and middle names i was given at birth. I was ecstatic! The agency reached out with letters and phone calls, finally getting my brother on the phone. He advised that he was not confirming anything until she told him exactly why she was calling. Well, we all know that she can't do that. So hello, impasse. Being a techno-geek, I began to scour the internet using the newly-gotten info. It took about a month, but I found her and my brother. I screwed up my courage and called him. I explained everything to him. He was overwhelmed and said he needed to think before he talked to me again. He called me the next day and let me know that he asked his mother about it, and she didn't deny it, but just shrugged her shoulders. He decided that he wasn't going to press her anymore. So while he accepts that I am his sister, she apparently will not acknowledge me. Anyone experienced this reaction? Finding her after 25 years and not being acknowledged feels pretty awful. :(