I am so sorry that you are being treated in the way that you are. It is especially hurtful from your own mother. THERE IS NOTHING WRONG WITH YOU!!!!! Who we love and are attracted to is not a choice. It is like saying I wish my skin color was different. We are who we are.
If you could maybe you could give your mother the web address for PFLAG. She is acting like this due to fear of what she does not know, or understand. Also, for your mom she is probably feeling like it is her fault in someway. More then likely that is how the "loving brothers" will look at it, and your mom knows it. You are going to have to give her time to even begin to digest what you have said to her.
In the meantime you have to take care of yourself. Being verbally abused is not healthy for you. Is there a possibility you have some other place to stay while this plays out? It might be emotionally safer for you. Also, if you are in a larger area there are support groups for gay and lesbian youth. I think it would be good to look one up. You need support right not. Just remember you are important, you are ok, I am thinking of you.
Leslie