Millions of people were separated during the 1950-53 conflict that sealed the division of the two Koreas.
Most died without the chance to see or hear from their relatives on the other side of the border, across which all civilian communication is banned.
The resumption of the reunions was among the agreements reached between North Korean leader Kim Jong Un and the South's president Moon Jae-in at their landmark summit in April.
Officials from both sides met at the North's scenic Mount Kumgang resort on Friday and set a date for late August.
"The reunion will be held from August 20 to 26 and 100 participants will be selected from each side," said a joint Seoul-Pyongyang statement released by the South's unification ministry.
South Korean officials will begin inspections of the Mount Kumgang resort -- the venue of the reunions -- from next week and the two sides will exchange their final lists of participants by August 4, it added.
Only about 57,000 people remain alive who are registered with the South Korean Red Cross to meet their separated relatives, and most are aged over 70.
For the lucky few chosen to take part, the experience is often hugely emotional, as they are given just three days to make up for decades of time apart, followed by another separation at the end -- in all likelihood permanent.
North Korea has a lengthy track record of manipulating the issue of divided families for political purposes, refusing proposals for regular reunions and cancelling scheduled events at the last minute.
Pyongyang has previously said it will not agree to family reunions unless Seoul returns several of its citizens, including a group of waitresses who defected from a restaurant in China.
It is unknown whether the defectors were brought up at Friday's meeting, but the two sides agreed to continue discussions on "humanitarian issues" through further Red Cross talks, according to the joint statement.
The rapprochement on the Korean peninsula was triggered earlier this year when Kim decided to send athletes, cheerleaders and his sister as an envoy to the Winter Olympics in the South.
Diplomatic efforts have gathered pace since then, leading to a landmark summit between Kim and US President Donald Trump in Singapore earlier this month.
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
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