Well, one unless your brother is under age, you don’t have much to handle. You should ask what the weirdness was about because there are a lot more steps before sleeping with one another that could be the issue. Don’t ever assume anything. It’s always best to ask questions and go from there. If this friend has been around the family for a long time it can be weird if your brother and friend do like each other. I get how weird it would come off, but be clear before you react.