I've always imagined Alec admitting his crush on Magnus like this. So I guess this could've been a little scene somewhere in season one

Isabelle's room was mostly black and pink. She had went through a lot to get her way to change up the room and add a small training area to it and couldn't bring herself to change the room around after that. The bed was a canopy, curtains hanging from all sides of it, and was a king size fit for a queen. Because the Lightwood home was roomy, her bedroom had tons of space for everything she needed....which was mostly wardrobes for her clothes. She even had her own walk in closet just for her shoes and dresses. Alec didn't want to say it but she was spoiled. Daddy's little princess. Being the only girl, she got whatever she wanted when she wanted it.

"So how was your day? I heard you had an adventure," Isabelle blocked his blow with her own staff.

"I had a very confusing day," he ducked as she swung her staff at his head. "How was your day? We don't really get to talk much anymore. I hardly have anything to lecture you about."

Isabelle brushed his hair off his forehead as they took a short break, which he leaned into like a cat getting its fur stroked. "My day was okay. Same old crap as usual. Was there something you wanted to talk about? You look frustrated."

Alec shook his head. "No. It's nothing. Are you going to attack or not?"

"Hey, it's okay. Listen to me," Isabelle took her brother's hands in her own before he could swing. "You know you can confide in me, right?" She smiled as Alec nodded. "I got your back, big bro. Izzy's going to make everything okay. Don't worry. Now think fast!"

Alec flipped over her blow and mumbled. He thought back to when they were kids and Izzy would train to help get his focus off the sound of their parents yelling at each other in the room next to hers. She'd done a lot of things to protect him growing up, and there was nothing he could do to pay her back but be the best brother he could to her. "Actually...there is something I want to ask you."

"I'm listening," she said. She scowled as her staff made a loud crack as it collided into Alec's. "Damn it. Okay. Now I'm really listening."

Alec backed away to rub the sweat from his face. "How do you know if you like someone?"

Isabelle spit out her mouthful of water she had drank from her water bottle. Some landed on Alec's face and he looked horrified at her. "Fuck. I mean shit. I mean-sorry. What? Why do you ask that?"

Alec shrugged. "I'm just curious."

"Uh huh. Sure, Jan. Don't ask who that is." Grabbing a tissue, she wiped her brother's wet face with it. "Okay. If I answer your question, do you promise to tell me what's really going on?"

Alec nodded.

"Good. Okay. Well....love isn't just set so that it's meant to be between one male and one female. Love is....difficult."

"Difficult?" Alec cocked his head. "I don't need any more difficulties in my life, Izzy. It's complicated enough as it is."

Isabelle ignored him. "How can I explain this....okay. You know how when I make cookies, all the cookies are different?" She waited for Alec to respond, which he did with a nod. "Let's pretend those cookies are people. Everyone is different. Some people are tall. Some people are short. Some are thin. Some are thick. Not all of them are the same."

Alec understood what she meant a little but it was still a bit confusing. "Everyone is different. I know that. But how are cookies relevant to my question?"

Isabelle beamed. "Love is different, just like people. Some girls may be attracted to men or women. Sometimes both. Same goes for men. But attraction doesn't end with just looks. You can be attracted to personality, their intelligence. Lots of things."

"Lots of things," Alec echoed. "How does someone know they like someone else?"

"That's a little more complicated. It's different with everyone. Sometimes you get along with someone right away. Other times you have to wait a while to see if there's anything there. Like feelings. You may like someone but they might not like you the same way."

Alec gulped. "And if they do?"

"Then that's great. Means you can explore your feels for each other. Go on dates and stuff." Isabelle raised an eyebrow. "You know you're going to have to spill the beans soon, right?"

Alec didn't have any beans. He scratched his head, thinking he should've brought some with him. "Real beans? Oh. Never mind. I know what you meant."

"It's an expression. Means you have to tell me everything that's going on in that beautiful mind of yours."

Alec groaned as she gently poked his forehead. "I have another question....what does love feel like? Does it have a specific feel to it?"

Isabelle blew a raspberry. "That's a tough one. Love is...." She smiled at her brother. He was watching her so intently that it was probably the longest time he's ever looked at her. "Love feels like how my cookies taste. Sweet and warm. No matter how bad your day, no matter how crappy you feel, you can come home to someone sweet and warm and they will do anything to make you feel better because all they want is to see you smile."

Alec thought about how their cookies tasted and widened his eyes. "Hard and burnt? That doesn't sound very appealing, Izzy. Great advice."

Izzy sighed as Alec pat her on the head. "Very funny, big brother. Now it's your turn to live up to the promise, Alexander Gideon. Why did you ask that question?"

Should he tell her? There was a million and one things going on in his head right now, and almost none of it made any sense to him. But then if he did tell her, maybe Izzy could help sort out his feelings. "Izzy? Don't tell mom and dad. Okay?"

Isabelle locked her lips. "Lightwood promise. Pinky swear." She held out her pinky like they used to do when they were kids.

Alec looped his own long pinky around hers. "Okay. This is hard for me. Okay...." He took a deep breath and sighed heavily. "I think....I think I have feelings for Magnus."

Isabelle shoved her free hand into her mouth to keep from screaming. "Alec! Are you serious? Like you like Magnus? For real?!"

Alec winced as her voice went up an octave. "Yes. For real. We shared a drink once. Felt something ever since."

Isabelle giggled uncontrollably and wiggled around on the bed as she sat down. "Oh my god this is perfect. This is my dream come true. I've literally dreamt of this moment since I saw you and Magnus for the first time together. I ship you guys so hard."

"Ship? What the hell does that even mean, Izzy?"

"Means I love the idea of you guys together. I'm calling it Malec. I dubbed it. Copyright. All rights reserved. Mine," she giggled again. "I knew something was up! When you asked me what love felt like, I just knew it. Alec.....I'm so happy for you. I really am. My middle child heart is just beating so fast for you."

Alec groaned as she hugged him, body stiffening. "Izzy. Stop. There's nothing wrong with me though, right? Will this feeling go away?"

"Big brother, you can like whoever the hell you want. There's no rulebook when it comes to love. Love is love. Regardless," she kissed his hand and smiled. "Have you told him yet?"

Alec shook his head. "No. Not yet. Too soon. I don't want to make things weird. For me or for him."

"Alec. The longer you wait, the harder it gets. Who knows? Maybe he likes you the same way?" She snatched his phone off the bed and scrolled through his contacts. "You really need to change your passcode. 1234 is way too easy."

"Iz? Wh-what are you doing?" Horrified, Alec tried to grab his phone from her grip. "No! Izzy! Stop," he groaned.

"Oh shut up. It's ringing! Here!" She laughed as she tossed his phone and he caught it.

"Hello? Alec, is that you?" A voice said on the other end.

Alec stiffened, phone pressed to his ear. "Magnus. Hi. Hello. Good afternoon?" He cringed as his voice cracked. Stupid Isabelle for doing this.

Magnus laughed. "Hi. What can I do for you? Is someone injured? Need to summon another demon?"

Alec glanced at Isabelle. She mouthed the words 'tell him!' while waving her arms around in the air. "Uh.....I....have something to tell you."

A pause. "Okay. What is it?"

Alec looked at his sister again. Isabelle bit into her pillow and waved him on. "Um......have you seen the weather outside? It's really sunny." He winced as Isabelle groaned and hit her forehead with a hand.

"That's more of a question, isn't it?" Magnus laughed. "Yeah, I'm aware of how nice it is outside. Are you enjoying the beautiful weather?"

"Yeah," Alec said, a bit too quickly. "Yes. I love sun. But I like the rain too."

Magnus chuckled. "I love a good rainstorm too."

They were both silent for a minute before Alec spoke up again. "I have to go now. I have training."

"Okay. Is that all you wanted to say? Just to remind me of the weather, I mean."

Alec nodded but quickly remembered he was on the phone. "Yes. That's all. Bye Magnus." He hung up before he could hear a bye back. He glared at Isabelle, who had a smirk on her face. "I feel like a freakin' idiot right now, Izzy!"

"I did you a favor. I stirred the metaphorical pot. Now I just have to wait for the ingredients to boil," she cackled like a witch. "My evil plan is working!"

Alec rubbed his arms and neck. "Izzy. I'm scared, okay? Very scared."

Isabelle stopped laughing. "Why are you scared?"

Alec swallowed nervously. "B-because mom and dad might not want me anymore if they know I like boys."

Isabelle's heart sank in her chest. Just like old times, she held Alec's hands in her own and leaned her head against his shoulder. "Remember when we were kids we climbed the tree in the front yard of our house in Idris and I fell and broke my arm?"

"Yeah. You cried when I snapped the bone back in place and used an Iratze." Alec remembered that day very clearly. He remembered the crack her arm made when she fell. He remembered how hard she cried and how he couldn't do anything to help because he thought he didn't know what to do. The most he could do was stay by her side before he used the healing rune.

"That's right. Do you remember what you said to me that day?" Alec shook his head at this. "You said it's okay to be scared. You said mom and dad weren't going to get mad at me because they loved me no matter what. Well, Alexander Gideon Lightwood. I'm telling you the same thing." She reached up and gently turned his head to face her. "It's okay to be scared, brother. Mom and dad aren't going to stop loving you any less for liking boys. You're their son. Their beautiful, intelligent son. It's impossible not to love you. You're Alec."

Alec smiled and let himself be hugged. As she hugged him, he could feel a stray tear threatening to roll down his cheek but he quickly caught it before Isabelle could see him crying. "Th-thanks, Iz. I feel much better."

"Glad I could help. Will you make me another promise?"

Alec stuck out his pinky again. "Lightwood promise."

Isabelle took his pinky in her own. "Promise me you'll tell Magnus how you feel. Don't bottle up those feelings for too long. Go for what makes you happy, okay? You deserve it."

Alec looked down at their entwined pinkies. Isabelle's hand was so small and delicate compared to his large hands. His knuckles were noticeably larger than hers and his fingers were nearly twice the length. "Yeah. I promise. As long as you don't grab my phone and call people without my permission again."

"I can't guarantee anything but I can certainly try," she giggled as Alec booped her nose like he used to do. "I love you, Alec. I love you so much."

Alec hummed low in his throat. "I love you too. So much."

"More than my hard and burnt cookies?"

"Definitely more than that," Alec whispered, earning himself his own boop on the nose and laughing along with his sister.