Kim Ki-sung, an 82-year-old South Korean, met his son and daughter whom he left behind in North Korea in 1951 when U.S.-led U.N. troops retreated during the Korean War.
"I am sorry for not taking you when I fled," Kim told his children in the emotional reunion, according to reports in local media. No foreign journalists were invited to the reunions at the Diamond Mountain resort on North Korea's east coast.
His son, Kim Jung-hyun, brought five medals he received from North Korean leader Kim Jong Il, the reports said. His sister said he received the medals "because he worked hard since he grew up without a father."
Kim Ki-sung was among more than 120 South Koreans, most in their 70s or 80s, who traveled by bus to the scenic resort for the three-day reunion.
Millions of families remain separated following the Korean peninsula's division in 1945 and the ensuing Korean War, which ended with an armistice in 1953, not a peace treaty.
There are no mail, telephone or e-mail exchanges between ordinary citizens from the two Koreas. They are unable to travel to the other half of the peninsula without government approval.
Family reunions began in 2000 following a landmark inter-Korean summit, but were halted by North Korea after conservative South Korean President Lee Myung-bak took office last year with a get-tough policy of holding the North accountable to its nuclear disarmament pledges.
The last reunions were held in October 2007.
North Korea agreed last month to resume the reunions as part of moves to reach out to South Korea and the United States after months of tension over its nuclear and missile programs.
So far, more than 16,200 Koreans have held temporary face-to-face reunions with relatives. About 3,740 others have seen relatives in video reunions.
A second group of reunions will begin Tuesday. It is unclear when they may be held again.