Jason Ronald Douglas was just 19 when he left his Queensland home.
Despite desperate efforts to contact him, his family says the next they heard from him he was a 36-year-old man living on the streets in the UK.
Mr Douglas moved to the English town of Milton Keynes in 1999 to live with his uncle, but lost touch with his family after witnessing the older man's death of a heart attack the following year.
His family say their prayers were finally answered when he was found living rough in the West Midlands about a week ago.
"I just talked to him like I was talking to him yesterday," a Queensland family member, who asked not to be identified, told AAP of their first phone call last week.
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"He cried a little bit and said 'I thought you didn't want me'."
The family member said they were desperate to get Mr Douglas home to spend time with his son, now aged 18.
"His son wants to finally meet his father," they said.
"We just want him home."
A Go Fund Me campaign has raised $2800 for his return.
Mr Douglas' cousin Lisa Andrews has told News Corp he stayed with friends for a while after his uncle's death but was later kicked out.
He had no phone number at the time and lost contact.
"We went through all of the police channels but we couldn't file a missing persons report in the UK because we didn't live there and the Australian police couldn't do much either," she said.
For years they had few leads until a relative recently went to English police, discovered Mr Douglas had previously been arrested and asked officers to pass on a message from the family.
A Facebook page dedicated to finding Mr Douglas includes comments from people sceptical about the story.
Supporters in the UK intend to meet with Mr Douglas to prove it's not a scam.
The Department of Foreign Affairs and Trade and police in the UK have been contacted for comment.
