So his mother should have a relative or ancestor who has blue eyes and his father definitely has?
either or, his dad could have brown eyes and have a relative who had blue eyes too. they just need two copies of the gene but it doesn’t need to be outwardly presented
His mom has a copy of the blue eye gene that she got from her parents (again, we don't know if they had blue eyes or just carried one copy of it. Both are possible) and for the dad, the only thing we know is that he has at least one copy of it. It it possible that he has 2 copies and therefore has blue eyes. With only one copy, he would most likely have brown eyes (there is a small chance for green eyes but they are rare in general and very rare in Asia). They also most likely share the same very distant ancestor, the OG blue eye mystery person who got the very first blue eye gene mutation... (genetics are weird and complex, that is but a summary and eye color actually is a combination of multiple genes but for blue eyes, you do need two copies of the gene that stops the production of melanin in the iris... anyway, I hope it makes sense.)
It is a recessive gene, which means that you need to recieve to copies of it to have blue eyes, so basically one from each of your parents. The parents might not have blue eyes themselves, they just need to have a copy of the gene. If both parents have brown eyes, the chances of getting blue eyes are very low. If both parents have blue eyes, then all children will have blue eyes. So, to conclude, we still don't know if the dad had blue eyes or not but Kwon inherited his from them both. It was team work.