The family have set up a fundraiser to allow some members to remain in Hamburg to look for him.
Funding is being raised to help towards the costs of trying to trace Liam, with over £6,000 donated so far.
Liam, who helped arranged the stag do as his brother’s best man, was last seen at 1:30 am in the early hours of February 10 in the Reeperbahn in the Hamborger Veermaster bar.
The group had splintered and believed that Liam had left before them, it was only the next morning when Liam was not accounted for that the stag party realised he may not have returned.
Some members of the family are in Hamburg handing out posters and leaflets in a desperate bid to try and find him, with police sniffer dogs being used as well as an online campaign.
His brother is due to get married in a few weeks time, but according to reports, his brother Eamonn has since postponed the wedding until his sibling is found.
Speaking to reporters, his older brother Eamonn said: “There have been a couple more potential sightings that the police are currently working on and reviewing CCTV on those areas.
“There is a recording of Liam in the Reeperbahn area.
“It isn’t actually outside the pub. It’s further along the Reeperbahn towards the train and subway stations.
“After that there is no other image of Liam. I don’t know the exact location. It’s some sort of gaming area, I think he was outside there.
“He is seen walking alone, as we thought he would have been.
“We don’t know much more at this time.”
“Please, please come home. Everyone misses you. You’re very much loved.”
“I don’t know what happened to you, just please get in touch, find a way.”
A Facebook and Twitter page have been set up and the family are appealing for anyone with information to come forward.
Hamburg Police have been searching the Elbe river and canals in the city.
Search dogs have been used and hospitals checked in the search and the Foreign Office has said it is assisting Mr Colgan’s family.