I apologize if I had any of the Spanish wrong, because I used Google translate and...yeah...
I also apologize if I had any of the ages wrong, so consider this as an alternative early life oneshot.

Leo was two when he first knew that he actually had a father.
"Mamá, mamá, ¿ya terminaste?" The two year old giggled, swinging his short legs.

Esperanza Valdez pecked her son on the cheek, laughing slightly. "casi, cariño. casi,"

Esperanza held a toolbelt, complete with pockets, wrenches, and equipment. She smiled sadly at the sky, knowing that it could only be complete with Hephaestus's blessing.

"Someday, cariño, you will meet your father. He is a great person," Esperanza said wistfully.

Leo Valdez giggled, holding up his hands, grabbing softly, mouth pulled into a smile. "I will meet papa!"

On Olympus, Hephaestus switched off his TV.

"One day you will, Leonidas," Hephaestus smiled sadly.  "One day."

Leo was eight when he first ran away.
Aunt Rosa roared in anger, as Leo told her that he failed his English test.

Rosa grabbed a pot and slammed it down on the counter. "I pay for you to learn, not to rot in a school! Go to your room! I don't want to see you! Disgrace," she spat venomously.

Leo fled to his room, burying his head into his hands.

Why does the world hate him so much? Why?

Leo grabbed a backpack and shoved daily necessities into it.

The world does hate him, but he's changing it.

He's running away.

As he ran down the road, bikes rang their bells as he almost crashed, cars honked, and Leo fled under a random bridge.

Leo sat down, grabbing a snickers bar.

"I'll find a home one day," he convinced himself. "One day."

Hephaestus blew the toolbelt from Rosa's home to bunker 9.

"He'll find the belt one day, bro," Ares clapped Hephaestus on the back. "One day"

Leo was ten when he ran away from his first foster mother.

"You are useless, I tell you!" Trim yelled, waving a beer bottle at his face, her drunk boyfriend passed out on the couch.

Leo cowered under her ferocious glare, unable to have the courage to speak back to her.

"Gah! Cat got your tongue? Rosa was so nice to keep you for months, too! A nice young woman, she is," Trim rambled, throwing the beer bottle aside. The bottle broke, shattering into pieces.

Leo gulped. He knew what he had to do.

He just had to run away again.

He'll settle down one day, he assured himself.

But when was that one day?

Leo was twelve, when he actually had a nice foster home.

"Leo! Time for dinner, mi valiente soldado," Clary Herondale called upstairs. (character credit to Cassandra Clare!)

Leo loved her. He also loved his foster father, Jace Heronadale. They had a big secret, and Leo was tired of it. He didn't want secrets anymore. From his dead mother, or foster parents.

"You'll know one day, mi valiente soldado," Clary would say everytime, "One day."

Jace taught him how to be a soldier. How to survive. How to be tough and not to back down.

Leo was grateful. He really was.

He's just tired of all the secrets.

"I'm coming, Clary!" Leo yelled back.

He felt guilty for doing this, but he didn't have a choice.

A loving, and caring home was just not the place for him.

He knew he wasn't normal.

I'll be back one day, mama, papa, Leo scribbled down on a note, I swear to god, you will see me again, no matter what. Los amo chicos. eras mis verdaderas figuras paternas. I promise. -----Leo Valdez.

Leo leapt out of the window, wind flying across his face as he ran away again.

"Leo? Where are you?" Clary opened his door, looking around in confusion. Her gaze landed on the note. "no."

"Jace!" Clary cried, "Leo's gone!"

Jace hurried up to Clary immediately. "What?"

Jace's eyes glided across the note steadily, a hint of wetness brimming in his pupils.

"I love you guys. You were my true parental figures," Jace translated, choking back a sob.

"He'll come back one day, Jace, he promised," Clary sobbed.

Both of them started to pray to the heavens, that their little boy will be alright.

One day, he'll come back.

Leo was 13, when his first girlfriend cheated on him.

"Eliza! Are you ready to go?" Leo asked his girlfriend Eliza.

Eliza looked up from her phone wearily. "I'm sorry, Leo, but I don't have time tonight."

Leo turned suspicious at heart—why doesn't she ever have time to be with him?

But Leo plastered on a fake smile. "Sure! That's fine."

Eliza smiled slightly. "Thank you for being understandable."

"No problem," Leo walked out his foster mother's house, to the mechanical shop where he was working as a student.

"Hey, Leo!" Vulcan greeted him with a lopsided smile.

"Hey, dude," Leo sighed.

"What's wrong, my man? Girl problems, 'innit?" Vulcan grinned.

"Yea. My girlfriend is acting weird. She barely leaves her phone alone, and she never has time again for me. She just turned down a date," Leo rubbed his temples.

Vulcan cocked an eyebrow.

"Oh, that's horrible. You should investigate what's going on, m'boy," Vulcan advised him.

"Really?" Leo looked up to Vulcan.

"definitely! I'll let you go half an hour early today," Vulcan smiled.

Leo grinned. "Thanks, fire dude!"

Hephaestus nearly broke the moment he heard Leo call him fire dude.

"Yes, m'boy, now go to work! Shoo!" Vulcan/Hephaestus ushered Leo out the door.

--------time skip to 6 pm--------

Leo waved goodbye to Vulcan. "Bye, fire dude!"

Vulcan/Hephaestus waved back at him.

When Leo got back home, his heart shattered into a million pieces.

His girlfriend was sitting on his bed, making out with his best friend, Tyler.

Both of them continued without a care in the world, moaning words of encouragement to each other as things got even more heated.

Both of them didn't even notice him, when they started throwing their clothing away, eating each other's faces.

Leo didn't bother to stop them. He ran into the living room, grabbed some Mars bars, and threw the key onto the coffee stand.

His heart shattered even more when Eliza started spluttering out Tyler's name, moaning and panting.

He knew what was going on. He couldn't even care any more.

He trudged back into his room, where Eliza and Tyler were doing the diddly-doo, and he flipped them with a middle finger, screaming "FUCK YOU!"

Eliza gasped, and covered herself with his blanket. "I swear, Leo, this isn't what it looks like----"

Leo's voice broke. "Yeah, like I didn't hear and see you having sex with my best friend?"

Leo ran away again.

He'll find someone one day.

That's what he told himself.

Leo was 15 when he first met Piper McLean.

"Yo! You new here? I can show you around!" Leo sauntered up to a brunette, his hand gesturing for a fist bump.

Brunette's eyebrow quirked. "I like you. And yeah, I'm a new student." Brunette returned the fist bump.

Leo led her through the school, both of them instantly becoming friends.

".......And that's the gym, more like torture prison, though, and that's the cafeteria, and the food sucks too. The dorms are over there, split into male, and female, which is a shame, I say. And that's the 'popular group', or whatever," Leo rambled.

Piper, the girl, laughed.

Leo knew that they would be incredibly close, and he was right.

He finally had a friend.

Timeskip 20 years later

Leo was 35 when he met his foster parents, Clary Herondale and Jace Herondale again.

But he turned different.

He had a son. He had a wife. He had friends, a home, and everything he could hope for.

He's even becoming a god when he dies, for gods sake.

But he missed those two a  lot.

Really, really much.

Leo knocked on their door tentatively. "Uh, is Clary Herondale and Jace Herondale here?"

The door swung open, revealing a mop of bright red hair, streaks of grey running down. The woman stood in front of him stood with confidence, strength, and stamina.

Leo recognized the woman as Clary Herondale immediately.

"Who are you?" Clary scanned him. Her face turned pale, and her eyes brimmed with tears. "God, are you---?"

Leo opened his arms widely, grinning. "Leonidas Valdez is back, mama,"

Clary let out a cry of joy and tackled him in a hug. A middle aged man, which Leo recognized as Jace Herondale stumbled out, holding a butter knife.

"Clary! And who the fuck are yo----oh my god," Jace stared at Leo.

"Leo, m'boy!" Jace tackled him in a bone-crushing hug. He flicked Leo's forehead. "Puberty's done great on you, aye!"

Leo laughed. "Jace, I'm 35."

Clary bombarded him with questions about his life.

Leo couldn't lie to them, could he?

He told them everything. the gods, the seven, demigods, heck, even dimensions!

But Clary and Jace didn't look even look a teeny bit surprised.

"To be honest, why aren't you surprised?" Leo waved his hands around.

Clary told him the lives of shadowhunters.

Leo understood why they kept secrets.

He finally understood.

He finally felt whole.

He finally felt at home.

The one day he kept talking about, kept convincing himself of, is finally here.

It's today.

Finally.

so, uh, hope you liked this!