One: Visitors, Steles, and Demons

Disclaimer: I don't own TMI or TID but the basic idea of this plot was mine :) Hope you enjoy reading this chapter!

Tessa was startled. Magnus had told her there was a young Herondale at the New York Institute, and she didn't know what to expect. It had been decades since she'd last met one of her descendants. Yet, here she was, face to face with a twenty-two year old man with black hair, blue eyes, and shocking resemblance of her late husband, William Herondale. He had just opened the Institute's door, surprised at having a visitor as they weren't expecting guests.

He groaned when he saw her. "Are you another one of Jace's admirers? He's not single! He has a fiancée!" The young man looked exasperated, and, turning away from the door, shouted into the corridor, "Jace! Stop letting women follow you home after our raids!"

"What are you talking about, Alec?" With the speed of a lion, another, twenty-one year old man with golden hair and eyes appeared in the doorway. "Hello," Jace began, "sorry about Alec. He tends to think that every lovely woman who nears the Institute is after me - rightly so - but I don't think I know you."

Tessa hadn't spoken a word since she arrived. She opened her mouth now to introduce herself, confused with all the conversation between the boys. "Hello, I'm Tessa Herondale," she began, a little uncertain as to what she should say. She looked at the two. "I lived in the 1800s, in the London Institute. I'm immortal, but that's another story. Sorry to turn up so abruptly, but my friend Magnus Bane has told me a descendant of mine and Will's resides here?"

Alec muttered under his breath something about Magnus loving a Will before him. Jace thumped him in the back. Tessa looked at the boys, expecting some sort of introduction. Always the more eloquent of the pair, Jace spoke up, grinning. "Jace Lightwood, the best Shadowhunter of our generation. This is my parabatai and adoptive brother, Alec Lightwood. He's still in shock that you mentioned that Will fellow. I recommend you don't do that, he's having boyfriend issues."

Tessa's eyes appeared to have widened in shock when she heard Alec mention Magnus loving Will. She made a mental note to question the glittery warlock about that later. "But Will—"

"Alec's about to go into cardiac arrest!" Jace warned Tessa, silencing her. The talking stopped long enough for Jace to usher the girl inside. She looked about twenty, with grey eyes and brown hair. When they were all settled at bar chairs in the kitchen (Jace was hungry), Tessa spoke again. "If you're both Lightwoods, who is the Herondale? I'd love to meet them— not that it's not been lovely meeting you two gentlemen, but—"

She was cut off by a twenty-one year old woman with jet black hair and dark eyes. She looked a lot like Alec, and she was quite pregnant. "Alec, can I borrow your stele?" she cut in, and, realising she cut a stranger off (although for what reason there was a stranger in her kitchen she didn't know), amended: "Excuse me. Alec, can I borrow your stele?"

Alec looked exasperated. "Iz, I know you're with child, but why don't you have your own? I lent you mine yesterday, and the day before—"

She rolled her eyes and turned to her other brother. "Fine. Jace, can I borrow your stele?"

The boys exchanged a silent look of annoyance, and Jace reached into Alec's pocket (Alec was quite surprised), pulled out Alec's stele, and handed it to Isabelle. She thanked Jace (and shot a pointed look at Alec), and walked off, heels clicking on the floorboards. Not even pregnancy could stop this Lightwood wearing her heels.

Tessa looked really confused. "Is she a Herondale as well?"

Jace responded, getting a bit annoyed with all of this Herondale business, "No. That's Isabelle, and she is a drama queen. If you're inquiring about my proper last name, then yes, it is Herondale. If that means that you're secretly my sister or something, then you'd better let me know quickly because the last time a family realisation drama happened my fiancée was my sister but she wasn't really and her real brother is a demon and we were bound together and almost got matching haircuts and—"

Alec silenced him with a shake of his head. Jace sighed, and Tessa looked proud. "Will and I are your great, great, great grandparents. Plus, it's obvious that the good looks remain in the family." (Alec blushed, perhaps in agreement, and Jace agreed with her comment.)

"Wow," was all the normally well-worded Jace could manage. Tessa pulled Jace into a hug he couldn't refuse.

However, instead of Alec being happy for the Herondales, he was still rattled by the constant mentioning of Will. He looked deep into his glass of water, as if it were a magic box which held all his answers. "Who's Will and why is my boyfriend so hung up over him?"

Tessa broke away from her descendant and looked at Alec, concern lacing her facial features. "Will is my husband. Was. He passed last century... He was a very great man and looked a lot like you. Welsh, but only used the language to curse," she smiled, "I wish you could have met him, Jace; I think you'd find that you're very similar."

"She didn't answer my question," Alec mumbled.

.

.

Jace walked over to the fridge and pulled out a container of leftover chocolate cake. "Did Izzy make this?" Jace asked his parabatai warily. Alec nodded and said, "With Simon. It was a disgusting display of affection, but I think he fixed it. It's edible, if that's what you're getting at."

Jace thought back to the day last year when Magnus discovered the spell that reverted Simon from vampire to a mundane again. Isabelle was so thrilled that he could enter the Institute that she asked him to move in (and share her bedroom.) After many months living together, Simon proposed, they got married, and they were expecting their first child in about a month.

The Shadowhunter had just swallowed a spoonful of cake when the door clicked again. This time, it was not his ancient relative (who was going to stay in the Institute with them for a while and was currently talking to Magnus in the library) but his fiancée, Clary, and her best friend and Isabelle's husband, Simon. They had just been out for coffee and to stock up on manga comics.

Jace greeted Clary with a kiss and Simon with a half forced smile and a, "Hello, Simon." He then proceeded to tell the two best friends about Tessa and her relation to him, and how she would be staying with them for a while. Clary looked thrilled by the end, and Simon looked like he was furiously trying to keep up. "Wait, so she's how old?!" Simon asked, shaking his head. Jace ignored him, taking Clary's bags to their room for her and leaving Simon to stare dumbfounded behind them. After living with him for a year and a bit, Jace had warmed to Simon —slightly— but sometimes his confusion was just really hard for Jace to be around.

He dropped her bags on the bed and, to her surprise, whisked her up in a hug and kissed her cheek. "How was the coffee trip?"

"Eventful," Clary kissed his mouth. He made a surprised noise— nothing ever happened when they went for coffee— and she elaborated. "We had just left Java Jones and we went through the alleyway—"

"Is that the alleyway in which you first stole my sensor?" Jace cut in.

"Yes. We went through the alleyway and we heard a shout from the dumpster. Of course, Simon had to go and have a look—"

"Bad move," Jace cut in again.

"That's what I said. He went for a look and it was an Eidolon demon in the shape of a young girl, and he went to help her—"

"By the Angel!"

"JACE! I'm telling a story. He went to help her, it went to attack, and I got it with that dagger you stuck in my belt loop before I go."

"So I saved your life today," Jace smirked, now lounging on their bed and pulling Clary down to sit with him.

Clary groaned. "I'm not finished! We turned to go and there Sebastian was, standing there with a creepy half-grin. He said, 'You, me, coffee tomorrow at one.' so I guess I'm going for coffee with my brother tomorrow."

"I was your brother for a while, so I'm going with you. He could try to hurt you again and—"

Now Jace was the one being cut off. Clary let out an exasperated sigh, and, "Jace!"

"He could try to give you a matching haircut!" Jace's eyes were wild. Clary rolled hers.

And so it was decided that Jace, Clary, and Sebastian were going for coffee the next day

A/N: That's the first chapter of what will be a full length! In future chapters, get ready to introduce Jace to Will and see what happens...

Please review! If you had a favourite line, feel free to leave that in a review too :) Hope you enjoyed it, thanks for reading!