Numerous testimonies of North Korean defectors confirm the practice of kin punishment (연좌제, yeonjwaje literally “association system”) in North Korea, under which three to eight generations of a political offender’s family can be summarily imprisoned or executed.
Horrifying, but not unexpected. I’m assuming most of the people that did leave at the beginning probably didn’t have family.
Considering how many people expected mass defections, I’d say it’s very unexpected for people who have not the sightliest clue about NK.