a/n: for those of you who aren't too familiar with the Korean age system, I'll try to break it down from how I've understood it and written this chapter after.
When you're born in South Korea, they say you're already one year old instead of the way Western people say you're zero years. Therefore, when in Western countries when you'd turn one, you're turning two in Korea.
Also, everyone gains a year at New Year's Eve, so basically at New Years Eve, you're two years older in Korean age than in Western age since you already gained first year and also the one you get on New Year. So on your birthday you don't say you just e year older, because you already did under the New Year, you simply just celebrate it on your birthday instead of everyone celebrating it on the same day.
Sorry if that's confusing and also huge apologies if I got something wrong, I'm both a terrible explainer and I might not have understood the concept of the Korean Age system completely. 

Word count: 199
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"You're getting so old. Soon the younger people will have to call you grandpa instead of older brother."
It was the 28th of March, which meant Jackson e year older than he already was. He had already adapted to saying he was 23, even though he was 21 at the end of 2015. That's just what happened when you live in Korea. 
"Aren't you charming? That's probably the nicest birthday greeting I've gotten today!"
Mark smiled. "I know right, I worked so hard on that one."
Mark loved teasing Jackson. The younger didn't become a variety star for nothing, he really did show reactions that weren't fake. 
"Will you tell me the same thing when I turn 50?"
"How do you know we're still together by then?"
"Mark, please, as if I were to ever let you go."
"Way to make me feel trapped, weirdo."
"You know you wouldn't leave me."
Mark smiled brighter than before.
"Why do you always have to be right?"
Jackson kissed the older. 
"I was born this way."
"Which I am forever thankful for."
Mark pulled Jackson in for a hug.
"Hold on...Why are you calling me grandpa, you're older than I am!"

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