Why did me so called friend lie to me about my brother?

Me and my brother don't talk anymore (live apart) but I needed to tell him something about a relative which was really important. When I mentioned needing to speak to my brother to a good friend of mine she said she hasn't seen him for years and he wouldn't be bothered about it anyway. I asked her why and she says, well that's Connor for you. I added him on facebook to talk to him, it came up with a list of mutual friends and things I have in common with him and my friend was a mutual friend. I clicked on my brothers wall and found a post from my friend to him saying would he like to meet up again which was about 6 months ago. In the mutual friends bit as well it also had her sister as a mutual friend. I asked them both about my brother and they said they haven't seen him for years like she said before and that he's bad news and that I should stay away from him and that any sane person would keep distance. I reminded them that im his sister and they just laughed and changed the subject. Should I be mad at them. What should I do??