What if Alec had told his parents about Magnus with Clary's Fearless rune?

"Try it on me," Alec said unexpectedly. "I could do with some fearlessness." He slid his jacket off, tossed it over the piano stool, and crossed the room to stand in front of Jace. "Here. Mark my arm."

Jace glanced over at Clary. "Unless you think you should do it?"

She shook her head. "No. You're probably better at actually applying Marks than I am."

Jace shrugged. "Roll up your sleeve, Alec."

Obediently, Alec rolled his sleeve up. There was already a permanent Mark on his upper arm, an elegant scroll of lines meant to give him perfect balance. They all leaned forward, even Magnus, as Jace carefully traced the outlines of the Fearless rune on Alec's arm, just below the existing Mark. Alec winced as the stele traced its burning path across his skin. When Jace was done, he slid his stele back into his pocket and stood a moment admiring his handiwork. "Well, it looks nice at least," he announced. "Whether it works or not…"

Alec touched the new Mark with his fingertips, then glanced up to find everyone else in the room staring at him.

"So?" Clary asked.

"So what?" Alec rolled his sleeve down, covering the Mark.

"So, how do you feel? Any different?"

Alec looked considering. "Not really."

Jace threw his hands up. "So it doesn't work."

"Not necessarily," Luke said. "There might simply be nothing going on that might activate it. Perhaps there isn't anything here that Alec is afraid of."

Magnus glanced at Alec and raised his eyebrows. "Boo," he said.

Jace was grinning. "Come on, surely you've got a phobia or two. What scares you?"

Alec thought for a moment. "Spiders," he said.

Clary turned to Luke. "Have you got a spider anywhere?"

Luke looked exasperated. "Why would I have a spider? Do I look like someone who would collect them?"

"No offense," Jace said, "but you kind of do."

"You know"—Alec's tone was sour—"maybe this was a stupid experiment."

"What about the dark?" Clary suggested. "We could lock you in the basement."

"I'm a demon hunter," Alec said, with exaggerated patience. "Clearly, I am not afraid of the dark."

"Well, you might be."

"But I'm not."

Clary was spared replying by the buzz of the doorbell. She looked over at Luke, raising her eyebrows. "Simon?"

"Couldn't be. It's daylight."

"Oh, right." She'd forgotten again. "Do you want me to get it?"

"No." He stood up with only a short grunt of pain. "I'm fine. It's probably someone wondering why the bookstore's shut."

He crossed the room and threw the door open. His shoulders went stiff with surprise; Clary heard the bark of a familiar stridently angry female voice, and a moment later Isabelle and Maryse Lightwood pushed past Luke and strode into the room, followed by the gray, menacing figure of the Inquisitor. Behind them was a tall and burly man, dark-haired and olive skinned, with a thick black beard. Though it had been taken many years ago, Clary recognized him from the old photo Hodge had shown her: This was Robert Lightwood, Alec and Isabelle's father.

Magnus's head went up with a snap. Jace paled markedly but showed no other emotion. And Alec—Alec stared from his sister, to his mother, to his father, and then looked at Magnus, his clear, light blue eyes darkened with a hard resolution. He took a step forward, placing himself between his parents and everyone else in the room.

Maryse, on seeing her eldest son in the middle of Luke's living room, did a double take. "Alec, what on earth are you doing here? I thought I made it clear that—"

"Mother." Alec's voice as he interrupted his mother was firm, implacable, and not unkind. "Father. There's something I have to tell you." He smiled at them." I'm seeing someone."

Robert Lightwood looked at his son with some exasperation. "Alec," he said. "This is hardly the time."

"Yes, it is. This is important. You see, I'm not just seeing anyone." Words seemed to be pouring out of Alec in a torrent, while his parents looked on in confusion. Isabelle and Magnus were staring at him with expressions of nearly identical astonishment. "I'm seeing a Downworlder. In fact, I'm seeing a warlock." He looked over at Magnus with a smile on his face. "I'm seeing Magnus Bane."

"Alec," Maryse said, hoping that what her son was saying was all some sort of horrible joke.

Alec didn't seem to catch the warning tone in his mother's voice or obviously didn't care, moving over to stand in front of Magnus. "I love him."

"I love you, too," Magnus whispered with a smile, bringing the Shadowhunter closer with a kiss planted on his lips.

"Looks like the cat's out of the bag," Jace whispered to Clary, who stifled a small giggle. Isabelle smiled, glad her brother had found someone special to him. Maryse and Robert stared at the warlock passionately making out with their eldest son, not able to say anything.

(((END)))

Yes, the whole thing except for when Alec said "warlock" came directly from the book. I take no profit from it and it belongs to Cassandra Clare from the second book, City of Ashes.

I loved this chapter, though. It was a lot of fun. Hope ya'll had fun with it, too! XD