Frank O'Neill attended Dublin's annual Missing Person's Day to talk about his brother James who has been missing since 1947.

O'Neill believes his brother James (or Jimmy) may have stowed away on a ship to America.

Speaking to journalist Alison O'Reilly, O'Neill said he had previously heard of a man with a similar name working in New York.

O'Neill told the reporter that at Christmas time, 71 years ago, his then-16-year-old brother "vanished" from their Waterford home.

His parents, Jim and Bridget, and four siblings (Frank, Nancy, Jack, and Noel) never recovered from the "pain and loss."

Read More: Family's desperate plea to find missing Irishman in New York

O'Neill (above) was four-years-old at the time of his brother's disappearance, "still believes there is a chance is brother is alive and well."

Speaking to the Irish Daily Mail, O'Neill said he was appealing to social media users, in particular, to help find his brother.

Read More: Irishman's 70 year search for brother who could have ended up in NYC 

"I think it’s the only way nowadays, social media and DNA testing, they are the way forward with these things," O'Neill told the outlet.

"That is the way a lot of people are getting their information. I don’t have a clue what happened to him. I was the youngest of four and I grew up in a house full of grief. It never goes away. People say to you, why don’t you just forget him. No one knows what it’s like, you can’t forget, that is the whole thing with missing people. They are missing. You can’t forget."

OK ppl. I need a huge favour. Can you please share this article/photo on your timeline. It doesn't matter where you...

Publiée par Denis O'Neill sur Vendredi 15 janvier 2016
Jimmy worked for a shipping company in Waterford at the time of his disappearance, so it is suspected that he "sneaked" onto a ship bound for the US. The family had no idea why the youth would run away, unexplained.

"I was only 4 when he went off, he was 16. He just went, he just vanished. He was working in a shipping company. I don’t know how long he was with them, we think he had an insight into stowing away, he used to go to the office on the quays and into the ships. I understood, the way people were talking, he went missing and stowed away that night, at 6:30 pm and he was gone more than 12 hours when the alarm bells rang. He ran away I think. I feel he did go on the ship," O'Neill said.

"That was the 15th December 1947, it’s a long long time to be missing," he added.

"My life could have been a whole lot different had it not been for this. I grew up with it. I was the baby, you can’t put it into perspective of what it consists of. I dread when I read stories about people going missing," he said.

"There was an element of grief in the house from the word go, I was the youngest of 7 children. Two passed. I have only one sister alive. It was horrendous. It never goes away. I’ve tried Australia, America, and there recently, someone gave me a note that was on the shipping manifest that went from Liverpool to New York. I thought I was on a winner."

According to O'Neill, on the manifest for the ship the 'M.V. Georgio' (above), there is an entry for a James O’Neill in 1952.

"There was a James M O’Neill on it. I thought I had a breakthrough. The age was right the name was right. But it ran cold. His destination was New York, the age is the same. We tried to find him. I’d love to find him."

Despite having a friend help him research, the search was ultimately fruitless. O'Neill's sister, Nancy, lived in New York for three decades and was also unable to find a trace of their missing brother. 

O'Neill added that a recent DNA test also proved futile.

Journalist O'Reilly writes that there are 870 people currently missing in Ireland.

At the poignant Missing Persons Day, Forensic Science Ireland stated that DNA testing is a vital part of tracing missing people. 

Dr. Dorothy Ramsbottom told those in attendance that she and her team are currently working "every week" on the identification of human remains.

If you have any information relating to this case, you can contact Frank O'Neill via his "Help Find James Malachy O'Neill" Facebook page here.

Read More: A year on, Australian town of 11 people still disturbed by disappearance of Irish pensioner