
You can't blame him for being childish when he is being treated like a child and it is understandable, especially in Asian setting. The youngest gets to be pampered while the older ones are always told they got to take care of their youngest. You can see it in their behaviour too. The sister wants to handle her younger bro's business and cover his ass in front of their mom. The older bro too is talking about giving allowance to his younger brother and even specifies he doesn't want to do it till he is pushing 50 which may seem odd but in Asian household its not that odd. I know a family who took in the husband's sister and they have been living like that for over 20 years now. The sister doesn't work but she helps around the house and with the family.
The problem here is he hasn't been out of the shelter a lot but during that trip where they got their money stolen he showed incredible maturity which shows he is capable of it, just needs a bit more growing up to do.

As a youngest and asian I kinda agree and disagree. Definitely I am pampered as the youngest and only daughter. But the ignorant part goes to my brothers. I dunno maybe male genes or something. They are 90% of the time ignorant about the situation. And I have to break down to them what is happening around. I swear men are clueless about the most important things and how women feels.
I'm sorry but I have to say this. Jeongyoon is kinda stupid. And naive and immature. Childish even.