The look Alec gave Jace clearly asked if Jace had lost his mind. "I define sleeping with anyone while in a relationship as sleeping around or cheating actually." He allowed himself to pick at the bedspread when his fingers felt a loose thread. An eyebrow raised upwards at the name Damien, but he made himself focus on the next part.
"You started sleeping with him before our relationship and didn't think to tell me before I agreed to all of this. I agreed to do something that is completely new and is extremely confusing for me. I'm in a relationship with you and Mark, I'd like you to respect the relationship because this isn't just some, uh, fling for me."
This whole thing was serious for him. Part of him felt like Jace should have realized how serious Alec would take things since they grew up together. Okay, yes, different worlds, but they were still parabatai. They had lived through a lot of the same stuff and that meant his younger brother should have known!
His eyes widened in surprise as Jace nearly yelled at him. That wasn't why he had made that remark, he had been trying to make his brother realize how serious this whole thing was. "Damn it, Jace. I wasn't serious. Magnus shattered my heart and barely gave me a reason why, I'm not going to go running back to him."