CoFA- Chapter 11, page 226-227:

"His real name's really Jonathan—"

"Jonathan is Jace's name," said Isabelle tightly. "I won't call that monster by the same name my brother has. He's always going to be Sebastian to me."

Clary had to admit Isabelle had a point. She had a hard time thinking of him as Jonathan too. She supposed it wasn't fair to the true Sebastian, but one of them had really known him. It was easier to slap a stranger's name onto Valentine's vicious son than call him something that made him feel closer to her family, closer to her life.

"I see your point, but I feel bad calling him Sebastian, when the real Sebastian was murdered by him."

"Well, what do you suggest we call him?" Isabelle asked annoyed the conversation. "Sebonathan?"

"What?" Clary asked, looking at Isabelle with confusion.

"You know mundanes like to merge two names together and create a cute pet name for the couple? Like, Brangelina."

"How do you even know about that?" If Clary were a boat, she would be lost at sea.

"What about Jobastian?" She said, ignoring the question. "Or Jonastian!"

Clary made a face. "No. That sounds like congestion."

"Well, I don't see the problem with that." Isabelle scoffed.

"What about Jostan?"

Isabelle laughed. "That sounds like the name of the main love interest in a bad romance novel."

Clary laughed. "You read trashy romance novels?"

"No, of course not."

"Liar! You do! But where do you find time to read?"

"It doesn't matter Clary. What about Sonatian?"

"No. Sonny?"

"You know, I think that might work," Isabelle said. "It's similar to Sunny, which totally does not match his personality—"

"Can we just agree on Sonny?" Clary interrupted.

"Sure; Sonny," Isabelle affirmed, in a slightly better mood.

"I wonder if he knows anyone named Cher," Clary mused.

CoFA- Chapter 11, page 226-227 cont.:

Isabelle spoke lightly, but Clary could tell that her mind was working, ticking over various possibilities: "Anyway, I'm glad you texted me when you did. I could tell from your message that something weird was going on, and frankly I was bored. Everyone's off dong some secret thing with the Conclave, and I didn't want to go, because Simon was going to be there, and I hate him now."

...

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A/N: Much thanks to originofcheese.