How will I tell my brother I'm in love with his girl?

Since I was young, I used to be the second option when it comes to my parents. My older brother was the only person they could see. He was the best in everything. Nobody had seen my sacrifices and achievements. Sometimes, I doubt if I'm really my parents' child or I'm adopted. Their treatment didn't change until I decided to live by my own and start my own business. I ignored them and I had come to a lot of realizations. I realized I should start living the life I want, without seeking their attention. I realized I should not depend on other people but myself alone. Everything went well, but not until my older brother introduced her girlfriend to us. She seemed to notice I am not so close with my family. We became friends because she understands how I feel. She found my story relatable. Shenyang women are really good at making you feel noticed. We often spent time at the coffee shop, talking about life and stuff. By her side, I found my comfort zone. Slowly and surely, I fell for her. I knew this was wrong but I couldn't help it. How should I tell her I love her? How should I tell my brother about it too? Help!