Ok, your son is Luffy. Just for this story because I needed one and he's innocent.

-----------------------------------------

"Mama! Mama! Papa Ace fell down the stairs again he's not waking up!" Luffy cried as she ran towards his mother.
(y/n) only chuckled.
'Your falling for your son,' (y/n) chuckled.
"It's OK. Papa Ace is just asleep." (y/n) said as she patted the hat that was on Luffy's head.
"Oh, yeah. You never told me about you and Papa. Could you tell me?" Luffy asked as he wiped his tears.
(y/n) gave out a chuckle as she placed Luffy on the couch.
"Get comfy. This is long." (y/n) said. 

-------------------------------------

It was early in the morning, Ace and Marco were heading to work. About 8:00 in the morning. It was sunny for a winter day. It was like spring. Spring of love.  As Ace and Marco walked passed stairs that goes down Marco started to talk.
"Isn't it sunny for a winter day?" Marco asked as he turned to the left to see nothing but Ace rolling down some stairs.
Marco only sighed as he watched the figure roll down the stairs. But then panicked when he saw a (h/c) haired figure go past. Ace crashed into her making her fall backwards. But before the figure could hit the ground a pair of hands stopped it.
The figure had one knee on the ground and his face was like 10 cm away from (e/c) eyed girl. The
girls face turned bright pink.

"I'm sorry, did I hurt you," Ace asked.
"I-i'm fine. Thank you. Are you OK? What happened?" the girl asked.
"I fell down the stairs for you." (Nice Ace, nice.)
The girl's face went from a hot pink into a strawberry. Ace only let out a chuckle.
"What is your name?" Ace asked.
"(y/n) (l/n), you're the magician. Fire fist Ace?" (y/n) asked with a smile.

Ace blushed but replied with a nod. This continued for more than 365 days. On the 366th day though lot's changed. On the 366th day (y/n) walked past the stairs but didn't meet a tumbling Ace but an Ace with a suit.
"Good morning Ace. Who are those flowers for?" (y/n) asked.

That was when Ace tried to take a step but the tripped down 3 stairs and face planted while flowers over his head so it doesn't get ruined. (y/n) chuckled before helping Ace up. Ace quickly rubbed his nose before commenting with a blush.
"Seems like I kept falling for you every day." Ace chuckled.
(y/n) chuckled as she nodded. Ace then shoved the bundle of flowers in her hands.
"Huh?" was all came out.

"So please could you please date me?" Ace smiled. 
"You don't know how many days I waited for this."
Ace hugged (y/n) and so did (y/n).
"You're my pencil," (y/n) muttered.
"Why?" Ace asked.
"Because you're going to re-write my future."
"Or is it because I'm going to mark you tonight?" 
It was a perfect couple. Nothing changed within them. Even in the wedding. Ace tripped with (y/n) in his hands. Even in the apartment, Ace fell for (y/n). 

-----------------------------------

"That's what happened." (y/n) ended the story.
But Luffy was nowhere to be seen. Ace was not sleeping on the stairs either.
'Where might have they gone,' (y/n) thought as she stood up to go look at the second floor. When she stood at the bottom of the stairs she found Ace cuddling Luffy towards his bed. (y/n) smiled but in a blink, Ace was falling backward. (y/n) panicked. Ace curled up into a ball and rolled backward. It hit (y/n) but that was nothing. They were actually very awake. Both of them were smiling like a madman.
"WE FELL FOR YOU!" they said in unison.
'Literally.' (y/n) thought before hugging them tightly.
"You people really are my pencil." (y/n) said as she hugged them both.
"Mama! Can I mark you!" Luffy said. 

(y/n) nodded. Luffy then started to draw on (y/n)'s (s/c) skin. Ace pouted he saw Luffy do what he wanted to do. Ace then looked at (y/n) who was using one of her hands to cover her mouth and her face going pink. She was trying to stop her laughter. That's what Ace thought until he saw where Luffy was drawing. On top of a hickey. Ace smirk widened.
"You are definitely going to meet a beast in bed today." Ace whispered before leaving.
Ace only got a smack on the head.
"Papa Ace is going to turn into a beast!" Luffy screamed before running away.
"You scared him!" (y/n) pouted as crossed her arms.
"It was a punishment for him taking you. You're going to get one too. Don't worry." Ace smirked before leaving.
"Scary...."
Luffy then was standing in front of (y/n) for rest of the day because he didn't want his mother get punishment because of him.

----------------------------

Sorry for the last part. It was too short if I didn't add it. Thanks to my perverted friends.