I'm pretty sure the implication is that the mom was also cheating, and his brother is the product of HER affair, just like he's the product of the dad's affair.
Which would actually make them not even brothers at all. Makes sense since there's been multiple comments of how they "don't look alike, even though they're brothers".
OMG that makes sense!! Thank you so much!!
oh damn that's wild
Exactly!!
They dont even look alike.
Guys can someone please tell me what mr. Kim told him and what is implied there? My braincells died today.