At its peak, there were about 50 or so households that lived in the village between the mid 1850's and Japanese colonial period. However when Korea was liberated from Japanese colonial rule there were only 20 or so households left.

On November 18, 1948 an order went out that all villages located in Jeju's mid-mountain range (제주도 중산간) must be evacuated. Suppression forces took particular interest in Youngnam-dong (영남동) because they had judged that members of the armed resistance were moving between the forested areas of Halla Mountain (한라산) nearby.

At that point there were only 16 households left in Youngnam-dong. However, despite the order to evacuate, only one household permanently left Youngnam-dong. Most of the others believed that the evacuation order would not last that long and they would soon be allowed to return to their homes. As such they instead opted to seek refuge in the nearby caves.

However, the order did not end quickly of course. For the next 2-3 months the suppression forces went back and forth through the area. They burned down the village and shot and killed whoever they found. Not only was the actual village of Youngnam-dong destroyed, but many family lines were completely ended as well.

References

Jeju 4.3 Archives - "영남동" (readable here in Korean)

Jeju Dark Tours - "Youngnam-dong" (readable here in English)