If these POWs do in fact defect to South Korea their families back in North Korea will likely face punishment by being sent to labor camps:

The government said Seoul has not changed its position regarding accepting to the nation, North Korean soldiers held captive by the Ukrainian military in the Russia-Ukraine war should they wish to defect to South Korea.
An official at Seoul’s foreign ministry said on Tuesday that the North Korean captives are considered prisoners of war, regardless of Pyongyang’s acknowledgement of their deployment.
The official added that in accordance with the 1949 Geneva Conventions, they must not be repatriated against their will to their home country, where they could face persecution.
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