Logan and Remus used to date before dealing with intrusive thoughts. They, eventually broke up, Logan better able to hide his feelings that the other. The two still felt something for each other, but Logan would always dismiss it whenever Remus showed up, wanting to get back together. Now, here Remus is in DWIT, and Logan is trying his best to stay calm. You see, this is how Logan knows so much about Remus, and what you should and shouldn't do around him. And that's why Remus is being a salty bitch while shamelessly flirting with Logan.