Sirius didn’t want to get their hopes up, since Remus turned them down when they asked him out. It was confusing. Remus constantly stares at them. He definitely flirted with them when he was drunk. And, he was so adamant that Sirius didn’t think he was dating Regulus. Sirius has plenty of experience with people being interested in them, and Remus was definitely showing signs. So, they weren’t going to get their hopes up, but maybe they wouldn’t give up just yet either. 