"The kidnappers now have a new demand, the release of Sheikh Mohammed Ali al-Moayad and his companion Mohammed Zayed," the tribal source told AFP.
The two men, who are from the same tribe as the men who seized the German family on Sunday, are still being held in US custody despite an appeals court overturning their convictions on terrorism charges in October.
Both were arrested in Germany in 2003 and extradited to the United States, where Moayad was initially sentenced to 75 years in prison and Zayed to 45 years.
Yemen has repeatedly called for the release of the Moayad, 60, and Zayed, 34, who after the court ruling were put under the jurisdiction of another judge and could be retried.
The US court said their convictions for giving financial support to Al-Qaeda and the Palestinian Islamist group Hamas were based on "highly inflammatory and irrelevant" testimony from third parties who had unfairly influenced the jury.
A tribal official said initially that one of the kidnappers was demanding $200,000 to recompense him for lost land and that police release his brother and son who were arrested four months ago over a land dispute.
The three Germans were being held in the Bani Dhabyan region about 80 kilometres (50 miles) east of Sanaa but the abductors moved them after a military helicopter searching for them flew over their hideout, a tribal chief said.
Yemen, the ancestral homeland of Al-Qaeda chief Osama bin Laden and one of the world's poorest countries, is a tribal country awash with weapons.
Tribes have abducted more than 200 foreigners over the past 15 years in a bid to extract concessions from the central government whose writ extends with difficulty over the lawless countryside.
All foreign hostages have been freed unharmed except for three Britons and an Australian seized by Islamist militants in December 1998. They were killed when security forces stormed the kidnappers' hideout.
In December 2005, armed Yemeni tribesmen captured a former German ambassador and foreign ministry number two, his wife and three children and held them for about five days.