Responses
The reason he didn't do that is because he had the same beliefs as the people he wanted to protect them from. He probably felt unconsciously ashamed of it, so he decided to try to stop the relationship without being pointed out as a hypocrite.
I'm truly disappointed by Greg's behavior. He could've handled the "problem" without lying, and actually try to verify if the couple was aware of the future problems a gay couple could face in Korea.
And also, I can understand trying to protect your family member because they're going. But now both of the people in the couple are adults. It's not your role to divide them, you have no say in their relationship. Even more after having said such a lie to your younger brother.