The brother of missing Kildare man Trevor Deely said they have identified a man seen in footage the night he disappeared.
It comes as the families of missing people gathered earlier for a ceremony in Croke Park to mark National Missing Persons Day.
22-year-old Trevor Deely vanished in the early hours of December 8th, 2000 following his Christmas party in Dublin.
Trevor attended his work Christmas party at the Hilton Hotel in Dublin 2, and then went to Buck Whaley's nightclub on Leeson Street which he left between 2.30am and 3.25am on the morning of December 8th.
The weather was extremely wet and there was a taxi strike in progress.
At 3.35am, Trevor called to his place of work - Bank of Ireland Asset Management Offices at Fitzwilliam Place - where CCTV footage of the rear entrance showed an unknown man talking with Trevor at the back gate.
Trevor was last seen on CCTV passing a Bank of Ireland ATM on Haddington Road at 4.14am.
Some 31 seconds later, a man was captured on CCTV walking in the same direction as Trevor.
In 2017, Gardaí released images of a man speaking to Mr Deely at his workplace on Wilton Terrace, and they then thought the same man followed him down Haddington Road.
Trevor's brother Mark has said there was nothing sinister about it.
"We've had all that footage cleaned up, we've had it cleaned up to a degree that the Guards were able to identify this individual," he said.
"They've interviewed him, and they're happy that he is not following him."
Deirdre Jacob disappeared in Newbridge, Co Kildare in July 1998 and her case was upgraded to murder in August 2018.
Deirdre was a trainee teacher from Newbridge, and had returned home from London for the summer.
The then 18-year-old went missing shortly after 3pm on the afternoon of July 28th, 1998 after she had been visiting her grandmother a short distance from her home.
The last sighting of Deirdre was as she reached the gateway to her family home after a 25 minute walk from Newbridge town.
Her parents Michael and Bernie said it never gets any easier.
"It's just another day; having said that it is nice to come together with other families who are in a similar situation," Michael said.
"It doesn't really matter which day it is, because Deirdre's missing every day," Bernie said.
"I suppose particularly at Christmas and other family gatherings, she's not there," she added.
There are around 900 long-term missing people in Ireland.
Additional reporting: Jack Quann