Your little brother, Hwang Hyunjin who has a phobia of being forgotten which is called, athazagoraphobia.  You had a meeting and had to leave Hyunjin alone in the house.  Your guys parents went over seas for a honeymoon, so it was only you two.  But when you came back home, you heard

Chan woke up down the staircase, his back and head hurting. It was only after some time he understood he fainted. Keeping it to himself, he hadn't expected the others to find out. Or Chan forgot he had a loving family and said family would make sure he always remember that.

Seongwoo didn’t know how he ended up being cared for, pampered and spoilt by Daniel and now resting his head on his lap as he felt Daniel comb through his hair, sometime feeling at ease as the younger gave him some gentle massage on his temple.   Whatever it is, he loves it. Every single one of it.

Imagine yourself getting sick and GuanLin spending his time to take care of you.