From Lee Min Seon’s blog at kakaostory : https://story.kakao.com/msnala/hOuuqs0BB7A
I had thought at first that this blog belongs to the child actor as it’s filled with his photos from various events and filming but the content level seems to be written by an adult and the boy’s name is Hyeon Jun.
The blog writer is probably someone related to him or a family member.
If I’m not mistaken, the boy plays Nam Jeong Gi’s son.
Im Ha Ryong is Nam Jeong Gi’s father and Chan Sung his brother.