<human>: My girlfriend and I have been best friends since childhood , but only started dating when we were in our senior year of high school. For some unknown reason my brother just hates her guts and always has, even as children,and  no one has any idea why. He'll say really hurtful things to her and then deliver some half apoplgy when myself or our mother gets onto him.

Recently he crossed the line by throwing it back into our faces that we can't have kids and that I was going to marry a "useless bitch," and that I should find someone better. I stood up for my girlfriend and told him to leave, but my girlfriend is still really upset. She asked me to basically cut ties with him, but he's my brother. 

I don't know what to do or how to handle this. I love my girlfriend to death and want to spend the rest of my life with her, but I love my brother and he's family. Can anyone offer advice?

Can you summarize the given text in a few sentences?
<bot>: My older brother hates my girlfriend for no reason and she wants me to cut ties with him, but he's my brother and i don't know if I can.