Sehun and Jinri were six when he and his parents found her rummaging through a garbage can on the sidewalk. They found out she's schizophrenic.
Sehun and Jinri were seven when she was never claimed and was legally adopted by them.
Sehun and Jinri were eight when they became best friends.
Sehun and Jinri were eleven when they became inseperable.
Sehun and Jinri were twelve when she claimed to have made a new friend.
Sehun and Jinri were fourteen when she announced she and Chanyeol were now dating.
Sehun and Jinri were fifteen when he realized he never heard of him before.
Sehun and Jinri were sixteen when he thinks Chanyeol is just an imaginary friend.
Sehun and Jinri are eighteen and he finds out he is very much real, and he may or may not live in their home.