The brothers are among a group of eight foreigners with suspected links to al-Qaeda who are facing terrorism charges in Yemen over an alleged plot to smuggle arms to Somalia.
The federal government confirmed yesterday that two Australian-born men and one Polish-born Australian citizen were being held on unspecified charges.
Sydney lawyer Adam Houda says his clients have done nothing wrong.
"We're talking about two kids here, one's 18 and one is 20, innocent of all claims or any links with terrorism," he told ABC radio today.
"They were simply over there studying."
Reports that the men were studying under religious leaders with links to al-Qaeda were wrong, he said.
"The university that's been mooted is not the university my clients were attending," he said.
Claims that they had links to al-Qaeda were "totally ridiculous".
"I take those claims with a grain of salt," Mr Houda said.
Mr Houda was reluctant to discuss the brothers' links to men who reportedly helped set up a Jemaah Islamiah (JI) cell in Australia.
Fairfax newspapers reported security sources had suggested that some of the three men arrested in Yemen had links to the Ayub brothers, the two Indonesian men who set up a JI cell in Australia in the late 1990s.
"There could have been some links but I'm not at liberty to discuss the detail. What I can say is: any type of link is all innocent," he said.
Mr Houda accused the Australian Security and Intelligence Organisation (ASIO) of targeting his clients because of their associations.
"On the way to the airport, at the airport they were interfered with," he said.
"What I mean by that is they were spoken to by ASIO people who, for some reason, have them under suspicion, because they may have some associates.
"They went over to Yemen and were all of a sudden nabbed by authorities other there."
Consular officials are trying to make contact with the men but they have been told by Yemeni authorities that the Australians are in good spirits and health.
Mr Houda said it was disturbing that the families hadn't been able to make contact with the men.
He urged the government to do its utmost to get in touch with the men.
"The Yemeni record on human rights is appalling and we are deeply concerned about their welfare," Mr Houda said.