I just need to point out I do not know the actual time the members joined BTS so I am just going with what I know.

The sitting room

Some time in 2011 Namjoon was at the dorm with His Hyungs and Yoongi who had just Joined.

"Hyung whats for dinner?" Asked yoongi.

"I don't know what do you want?" Asked one of members.

"Oh can we have sea ff?" Yoongi was going to asked for sea food but got stop by Supreme Boi.

"Shhh don't finish that word." He said.

"Why?" Asked Yoongi.

Supreme Boi Pointed to Namjoon. 

 "Yeah don't say that word in front of Namjoon. Said another member."

"Why?" Asked Yoongi. 

 "Well why don't you ask him and see what happens." Said another member.

 "Its fine we don't have to have seafood." Said Yoongi.

A few days later in Studio

 "Namjoon looks like we have to get dinner for just us two." Said Yoongi.

 "Alright." Said Namjoon.

"Should we go to the beach and get a few crabs?" Said Yoongi but was confused when he notice Namjoon  looked upset.

Namjoon got up and started walking to the door.

" Where are you going? Asked Yoongi."

"I don't feel well I'm going back to the dorm." Said Namjoon.

"Okay." Said Yoongi.

Namjoon left the studio.

Yoongi was confused so he decider to ring Supreme Boi.

 "Hello." Said Yoongi.

 "Hello whats up?" Asked Supreme Boi.

 "Namjoon just left and I feel like I've said something wrong." Said Yoongi.

 "You didn't ask him if he wanted crabs for dinner did you?" Asked Supreme Boi.

 "Yeah then he freaked out." Said Yoongi.

 "Yeah Yoongi you shouldn't have said that Namjoon has an obsession with crabs he finds them adorable." Signed Supreme Boi.

"Oh where do you think he be?" Asked Yoongi.

" Actually he's here come back to the dorm and you can apologise to him." Said Supreme Boi.

 "Okay." Said Yoongi.

2 months later.

"So this is the dorm." Said Hoseok.

" Yeah." Said Yoongi.

"Hello." Said Namjoon.

"Hello." Said Hoseok.

"Hoseok this is Namjoon." Said Yoongi.

"Nice to meet you." Said Hoseok.

"You two, Yoongi Hyung I'm going to the beach." Said Namjoon.

"Okay." Said Yoongi.

"What you doing catching us some seafood for lunch?" Hoseok asked.

 "No I like to look at crabs and just so you know to me fish are friends not food." Said Namjoon.

Namjoon Huffed and ran  out.

"Ah Yeah you shouldn't have said that." Said Yoongi.

 "What's his problem?" Asked Hoseok.

"There's one thing you need to know about Namjoon he loves crabs and gets upset if anyone mentions eating them." Explained Yoongi.

"So how do we have seafood?" Asked Hoseok.

"Just order it and then he can't complain." Said Yoongi.

"Okay" Said Hoseok.

A few months later

"So What do you guys want for dinner?" Asked Seokjin who had just arrived at the dorm a couple of days ago.

 "Can we have Japae and meat, please?" Asked Namjoon.

"Okay." Said Seokjin

"Hyung come with us please?" Said Yoongi and Hoseok.

"Okay." Said Seokjin.

In the Kitchen

 "What?" Asked Seokjin.

"You can make seafood but don't tell Namjoon." Said Yoongi.

"Okay, I actually thought about just doing what he wanted and going out later what he doesn't know won't hurt him." Said Seokjin.

"Wow your so smart Jin Hyung." Said Hoseok.

"Wow Hyung I'm not used to this yet." Said Seokjin.

A month later.

 "Wow thighs." Said 14 year old Jungkook.

 "I'm Namjoon." Said Namjoon.

 "Ah Jungkook." Said Seokjin.

"Jin Hyung!" Jungkook shouted.

"You two know each other?" Asked Namjoon.

"Yeah my dad knows his dad." Said Seokjin.

 "Jungkook are you hungry?" Asked Seokjin.

"Yeah." Said Jungkook.

 "Okay I'll cook just come here a second." Said Seokjin.

"Okay" Said Jungkook.
In the Bedroom

"Jungkook just so you know never ask for seafood in front of Namjoon. Okay." Said Seokjin.

 "Does Namjoon Hyung not like seafood?" Asked Jungkook.

"No and he as a love for sea creatures so don't mention anything in front of him you don't want to upset him do you?" Said Seokjin.

"No." Said Jungkook.

"Good boy." Said Seokjin.

6 months later

 "What's for dinner?" Asked Taehyung who had just moved in to the dorm.

"Whatever you want." Said Seokjin.

"Well can we have Japhae, please?" Asked Taehyung.

" We got similar tases the universe must be sending a message." Said Namjoon.

"Okay, Jin Hyung can I talk to you in private?" Asked Taehyung.

Seokjin and Taehyung go to the kitchen.

"What's up?" Asked Seokjin

"Namjoon Hyung weird." Said Taehyung.

"Yeah just don't mention seafood in front of him and he's fine." Said Seokjin.

"Okay." Said Taehyung.

6 months later.

 "So what's for dinner?" Asked Jimin who had just moved in.

"What do you want?" Asked Seokjin.

 "I'll have anything but seafood." Said Jimin.

 "You're like me." Smiled Namjoon.

 "Yeah I guess but why don't you like it?" Asked Jimin.

 "Fish are friends, not food that includes crabs and lobsters." Said Namjoon.

 "Okay I just don't like the taste." Said Jimin.

 "Oh okay." Said Namjoon has his eyes went downwards.

"Why are you upset Namjoon Hyung?" Asked Jimin.

" It's just now you said that it feels like a betrayal.! Said Namjoon.

"Hyung you are so dramatic." Laughed Jimin.

 "Yeah maybe." Agreed Namjoon.