An Australian biostatistics professor – who worked as part of Qatar's coronavirus task force – and his son are being detained without charge at a secret location in the country for almost five months.
Prof Lukman Thalib, 58, and his son Ismail Talib, 24, were arrested at their home in Doha in July.
Three months after their arrest, the US State Department named another of the academic's sons, who lives in Australia, as an alleged “financial facilitator” of Al Qaeda.
Prof Thalib has lived in Qatar since 2015 and was working as one of its leading public health officials on its pandemic response.
The father of four was the head of the Department of Public Health at Qatar University.
The first his family knew of his arrest was when they received a call from him in September. It is understood he is now allowed to make two weekly calls to them.
The Australian government is providing consular assistance to them and was first able to visit him last month.
His son Ismail had been working as a security engineer in Qatar for three years prior to his detention.
Prof Thalib's daughter, Maryam Luqman Talib, called on the Australian government to give them more assistance.
"We just need my father and brother back home where they belong. We have been deprived of their love and warmth," she said.
"During this ongoing ordeal, we have not received the support we needed from our government. We appeal to our fellow citizens to assist us in calling upon our prime minister, Scott Morrison, to take the necessary steps to secure my father and brother’s safe and immediate release.”
The government told the family it is still investigating why they are being held.
Prof Thalib completed his master's degree and doctorate in the UK and has been involved in more than 400 international research projects during his 30-year career.
In October, the US named Ahmed Luqman Talib as a terrorist financier and alleged that he used his gemstone company to move funds around the globe.
“Talib has had financial dealings in a number of countries, and his business dealing in gemstones has provided him the ability to move funds internationally for the benefit of Al Qaeda,” the State Department said.
After the announcement his home was raided by police in Australia.
He has not been charged with any offence.
The family lived in Brisbane before moving to Qatar.