Isabelle couldn't really figure out what she was doing here, curled up on Magnus and Alec's couch, waiting for Magnus to start explaining things to her. She had seen him storm out of the Institute, and when he hadn't been followed by Alec, she went after him herself.

Of course, Magnus had put up a fight, saying that he just wanted some time alone to think through things. He finally relented when Isabelle suggested that talking to someone might help him work through it. Now she was perched beside of him on the couch, wondering if she had made the wrong move.

She looked over when Magnus cleared his throat. She hadn't been prepared for what a mess he would be. She had suspected that he and Alec were having problems, after all, the only real problems they'd ever had had begun over the immortality insecurities of Alec; she knew that the thought of marriage was going to bring those insecurities to the front for both of them. But she hadn't really ever seen Magnus this way, and she knew that there had to be more to it than just the normal fights they'd had.

"I'm sure by now you've realized Alec and I aren't really seeing eye to eye on this marriage. But that's not exactly what I got so angry about."

Isabelle listened intently while he explained what Clary had just revealed to them as well as what had caused him to storm out on Alec. She, just as everyone else, was a bit confused as to what Alec had actually apparently done wrong.

"Magnus," she made sure to keep her voice soft and kind. "What's this really about? You and I both know that Alec didn't do anything to cause that reaction. At least, not from what anyone can see on the surface."

"Alright, Isabelle," Magnus was suddenly much more composed than he had been. "I'm going to explain something to you that I've never sufficiently explained to anyone, save Tessa Gray."

To that, Isabelle wasn't sure how to react. If this was something that even Alec hadn't heard, she wasn't sure that she wanted to get in the middle of it herself. But the longer she looked at Magnus and the more pain she saw in his eyes, the more she realized that Magnus needed her right now, as a sister. She rested one hand on top of his and smiled, indicating that he should continue.

She could tell that it took everything he had to continue without breaking down. "I've lived a long life, and most people assume that I've fallen in and out of love so many times that I'm used to the loss. Frankly, that just isn't the case. Sure, I've been with more people than anyone could really count. But out of all of them, I've only ever truly loved a handful." He closed his eyes for a moment, taking a deep breath, and Isabelle knew he had to be thinking of Alec in that moment.

"Throughout most of my life, I've only ever honestly dreamt of one thing. The only unrealistic thing I've ever genuinely wished for has been that someone who loves me would get the chance to be with me forever. And, yeah, I know you're thinking that Alec is getting that chance now. That's not what I'm afraid of."

Magnus closed his eyes once again and they remained shut when he continued talking. "I'm honestly terrified that he is going to decide that he doesn't want the rune, and this may be the most selfish thing I have ever said. But I have been told before that I am essentially not good enough to spend eternity with. That I am not enough to be given when immortality is in the mix. I am simply and utterly frightened that Alexander is going to feel the same way."

Both Isabelle and Magnus were startled when a third voice entered the conversation. "Who told you that? Who would say that about you?" They looked up to see Alec standing in the doorway.

Magnus finally allowed the tears to start flowing again. "Etta," He answered, his voice on the verge of breaking. "She meant nothing by it. She loved me, I do know that. But once she was gone the effects of what she said lingered. The more I thought about it, the more it hurt. You say you love me, Alexander, but she said that as well."

Alec looked terribly angry, and Isabelle couldn't tell if the anger was toward Magnus or whoever Etta had been. He turned back to the door and Isabelle thought he was going to leave again when he suddenly turned and strode over to Magnus. Alec crouched until his knees were almost touching the floor, so that he was eye to eye with Magnus.

"I am absolutely in love with you." The way he said it made it seem like each word was its own separate sentence, and Isabelle could hear the massive amount of passion her brother put into every syllable.

"You are decidedly good enough to spend eternity with. You told me that your two concerns were that I would either get bored with you or try to kill myself once I had lost everyone. Well, let me tell you that the reason I am hesitating to say yes is certainly not because of the first reason. The moment you said it, that thought was dismissed from my mind." He paused long enough to wipe a tear from Magnus's face. "I am simply afraid that I won't be able to take the pain once the rest of my family is gone. I'm afraid that I'm going to overestimate my strength and end up hurting you, which is the last thing I would ever want to do."

Magnus didn't hesitate a moment before he had found his voice again. "No, Alec. You are the strongest person I have ever met. If you were to set your mind to it, I honestly believe you could take it. And I would be there every step. But I don't want to be the cause of any of your pain, and that's what made me ask you to slow down."

Alec sat on the couch between Isabelle and Magnus, grabbing one of each of their hands on the way. What he said next surprised Isabelle more than anything that had happened that day. "Magnus, stop worrying about being selfish for once in your life. You're too worried about seeming selfish to simply tell me what would make you the happiest. So, please, for the sake of this relationship, be honest with me. What do you honestly want me to do?"

It was easy to see that Magnus was speechless. It looked as though he was struggling within himself, wanting to be able to do exactly what Alec had just asked him to do, but also wanting to do the complete opposite.

When he began, both Alec and Isabelle could barely breathe out of anticipation. "My Alexander, you have always been the selfless one. Always. And if I were to be absolutely honest with you, I would tell you right now that the only thing in this world that I want is for you to be by my side forever." He held up his free hand when he saw that Alec was about to conclude the conversation.

"As long as I am being honest with you, I simply cannot cause you any pain. And losing all of your family will cause you more pain than anyone should ever have to bear."

The world around Isabelle froze at what Alec said next. "Magnus, I will not have lost all of my family. You are soon to be part of my family, too. I will have you. Not to mention, I want to give you the one thing you've never asked anyone to give you. The one thing I know you've always hoped for but have never felt you deserved. I want to give you a family of your own."

That was when Isabelle's heart shattered at the sound of Magnus's sobbing.