I'm unnerved by some of my boyfriend's kinks. What should I do?
What kinks of his unnerve you?
I suspect he wants to have a threesome with his brother and me.
Partners are expected to keep an open line of communication when it comes to their sex life. If you're uncomfortable with his kinks, you should let him know. That way you both can find something that you feel comfortable in doing sexually together.
I'm going to pretend that I don't hear him.
You shouldn't pretend that you don't hear him, you should handle it and be honest with him about what you like and what you don't like.