What was their age gap again?? And whose older?

I guess if mr Kwon (blue eyes) is class of 2008 and the other one (black hair) is 2016 their age gap is 8 years :)

haebeom is older by eight years

Haebom is 36, Ho is 28 at the start of the story. Haebom had b'day in one chapter, so he is now 37, I guess. Ho is 29