Unforgivable Love (boy x boy)

I never thought this would happen. I didn't really believe in love, not at all. I surely never thought I'd fall in love. Finally, I do. My whole life turns around. But, I can't even tell the person I love. Why? Well, it's really complicated. I fell in love with my sister's boyfriend. What's even worse, I'm a guy. When he proposes to my sister, my heart breaks. I want to tell him so bad, but I definitely can't now. I love my sister so I'd never take the one she loves away. What am I going to do? Well, that's easy. Or, at least I'd hoped it would be.