It's a problem if people are posting novel spoilers without hiding them under spoiler covers and including text…
Unfortunately, temptation is too strong and willpower weak. I have also read the comments by people who have read the novel (under spoiler's tag) while strolling through the thread. It did ultimately spoil some of the enjoyment and I wished this series was based on original script. Don't blame anyone but myself. But maybe it would be better if discussion about the novels could be posted at the discussion section. Just a thought.
Subsitition. The real baek son has too many screws loose, so the switcheroo, grandfather dumped him. I think ML is actually the brother and not the son. This is all based on commenters here who has read the novel. Of xourse the novel and drama might diverge so take it with a small dose of salt.