Here was me struggling to find the plots for a few things when I tried to rewrite the book because I realized I had no idea what the ending should've been. Then realized there's no reason to finish because.. it wasn't worth it. They were step siblings too.. kind of weird so-
Plot twist : Your mom is actually kidnapped, by their father, who isn't their father, without their knowing, and everyone turns against each other. But RM
What they do / Why they do it: To fend off saesangs. Using hackers to fend off other hackers and saesangs. Gambling / Loan sharking for the use of hacker's money. Frauds found and kidnapped, abused to find out reason why, if they tell immediately, jailed. If not, executed. Loan sharking in unknown places, and adding recruits, blackmailed immediately if found why they are pretending.