Current Ages (KR AGE)

Hwang Ran - 26

Ryu Dong-Wook (Zen's older brother) - 24

Hwang Trang - 22
Kim Jihyun (V) - 22
Han Jumin - 22

Kang Jaehee - 21

Ryu Hyun (Zen) - 19
Rika - 19

Saeyoung (Seven) - 17
Saeran (Ray) - 17

Yoosung - 16

Ran is older than Jumin by 4 years
Ran is older than Zen & Rika by 7 years
Ran is older than the twins by 9 years

Jumin is older than Zen & Rika by 3 years
Jumin is older than the twins by 5 years

Jumin, V and Trang are same age
Rika & Zen are the same age
Yoosung and MC will be the same age

International (Int'l) Age

You are born at 0 years old. Takes into consideration your birth month and day. As far as I'm aware America, and most non-Asian countries are like this.

Korean (KR) Age

You're a year old the day you're born. Everyone gets older on New Years. Your personal birthday doesn't count your age, but can be celebrated though it's not as important as New Years. As far as I know there is a lot of importance put into age, there's plenty of terminology for this, it determines how you can talk with one another (formal speech or casual) and how you address other people. There's a level of politeness you need to adhere to when talking to someone older than you. There's even a term for someone that's the same age, which is 친구 'Chingu' which means friend or same age friend (I've seen this used as a translation before).

Noona, Unnie(Eonni), Hyung and Oppa for someone that's older than you depending on your gender.

You refer to your in-laws as well as your friends' parents as mother and father. (I don't think I've heard Mr. or Mrs. like in America.)

You refer to the elderly as grandpa and grandma. (Yes. Even if they are not related to you at all.)

I've also heard ajumma and ajusshi often which could be taken as madam and mister. Of course all these could be considered casual form or generic. There are other suffixes used to make it more formal depending on level of closeness and respect given.

There's sunbae and hoobae, which is equivalent to the Japanese senpai and kouhai. Usually used in a work or school setting. They basically mean senior and junior.

I'm sure there's a lot more, this is just the general information.

In Vietnamese, when it comes to family it boils down to how someone is related to you. (Why am I using Vietnamese as an example? Because I'm way more familiar with that than other Asian languages)

Example.

I have a cousin. She is the daughter of my mother's younger sister. So I don't have to call her anything special. You usually don't if you have an 'older rank' in the family tree. HOWEVER. Her father is my dad's cousin, who is the son of my grandfather's older brother's son. So her dad has to call my dad, Uncle, while I have to call him Big Brother. Since he's on the same line on the family tree as I am. (And it's not just because he's older than me, but because he's my grandfather's older brother's son; also your paternal relationship with someone outweighs the maternal relationship; at least that was how it was explained to me.) Whereas my cousin has to call me 'Aunt' and my dad 'Grandpa'. . . . Yeah. It broke my brain too. There are no freebies of just calling each other by name or simply cousins. Western culture is much more forgiving in this sense; you don't have to use so many brain cells to figure out how to address any given relatives outside your main unit.

Age of Majority

In America, you're an adult at 18 and the legal drinking age is 21. In Korea, you're considered an adult and can legally drink at 19.

Adoption

This topic is tricky and I took a lot of liberties with this. When I did my research I realized it explains why V was helpless in getting the Choi twins out of their situation. As far as my understanding goes, if the local adoption process is anyway similar to the international adoption process in South Korea, then the minimum age requirement to be able to adopt is 25 years old with the oldest being 44. On top of that it can only be heterosexual couples with no prior serious illnesses. In America, it varies depending on the state; with the minimum ages being 18, 21, 25 or 10 years older than the adoptee. Of course in all this the biological parents have to agree to this. In either case, there also needs to be a home study to make sure it's safe and fit for the child. These are the requirements even if you don't go through an agency and go for an independent adoption.

V is not rich on his own, he was born into it. It's really his daddy's money and if his dad doesn't support his decision then V is SOL which means bye bye money. Sure, he's a successful freelance photographer, but he hasn't been for long yet and it's not exactly considered a stable job. From experience, when any agency look at incomes solely based on commissions they tend to want evidence of a longer period of stable income than normal. He's young and unmarried. That doesn't make him look too good a candidate to be adopting someone, especially without the parents consent. Even if he used money to get what he wants, there's too many adverse setbacks afterwards.

Compared to Jumin, who's not only the heir to a huge conglomerate corporation, but he's already been working for the company for some time. It means his money ain't just daddy's money, and obviously he'd have stocks with the company. Even if Daddy Han doesn't hand over the C&R keys to Jumin, which is doubtful since he's the only son and heir, he can't take away what Jumin already has under his name: companies given to Jumin, buildings, homes, stocks and whatever Jumin finds interesting. He'll still be making money without having all of C&R under his thumb. If he really wanted to do something I doubt he'd be worried about losing his income or being cut off, and even if he did he would totally have a plan. Plus I doubt he'd have any scruples of getting his lawyers to make it happen somehow. 'Money makes the world go round' has been kind of his motto. No matter how the cookie crumbles, Jumin will always have money.

Zen's Real Name

Honestly I was confused with the order of this. Why? Because both Ryu and Hyun can be used as a last name in the Korean language. I mean when it's translated, usually it gets switched around which is First Name, Last Name. However, I usually prefer and am more used to hearing Last Name, First Name.

Also. I totally love hearing 'Han Jumin mida.' (TR. This is Han Jumin.)

Why was I confused? Because I remember at some point in the game, V calls Zen, Hyun. I didn't think V would choose to call Zen by his family name rather than his given name, because they should be a bit closer than that. V is older, he's somewhat close with Zen, and even acted as his guardian in the past to save him. It doesn't make sense to me he would call him by his last name. Anyways. It seems his given name is Ryu and family name is Hyun. For the sake of continuity I'll keep it switched in the story, making his first name Hyun and last name Ryu.

Why didn't Jumin adopt Zen too?

At this point Zen has already become an adult. Yes, it is possible to adopt an adult. At that point you just need the other person's consent. However, Zen is a special case. He's only known Jumin a few years by now, and he's come to see him as a knowledgeable and supportive older brother. He grew up with parents and a somewhat caring older brother. Zen doesn't really need a father figure in his life like the twins do.

Why did Jumin adopt the twins?

So many reasons.

But here is some non spoilery info dump.

There is a concept I've heard and personally experienced. 'It's one thing to think about it and another to have it said out loud.' Even if you thought it in your mind, there's a measure of 'it's not really true because it's never really been confirmed'. So you won't truly believe something until you have concrete evidence. Hence the saying 'seeing is believing'.

It's a way of saying I see you as my family, and not only do I want everyone to know it; I want you to be taken care of even if I'm not around anymore.

It may be a stupid piece of paper, but the sentiment, love, and care put into it is all there. This is totally something Jumin would do. I mean in canon, he even has a self made friendship contract with V.

End note.
That was a lot of information, but this story and AU world is kind of like my baby. I love it and can't help wanting to talk about it. I still have a lot to learn as a writer/creator and some concepts, ideas, or facts are hard for me to convey into my writing.

Thank you for your patience, for reading this story of mine, and enjoying this alternate world I created.