Zhejiang is a particularly Christian area of the country.
Wen Xiaowu and his wife and son were detained earlier in the week, the couple were charged with "gathering a crowd to disturb social order," and the son was charged with "obstructing public service."
Both parents provided legal defence counsel for churches affected by an ongoing cross demolition throughout the country.
According to anti-persecution group China Aid their family members think the detentions are a response to the couple's meetings with officials from the US Consulate in Shanghai and a number of foreign journalists.
During the meetings its thought the campaign of cross removal was discussed.
The Chinese authorities say the cross removal is due to health and safety reasons.
It comes less than a week since Chinese President Xi Jinping warned Chinese people away from religious influences and infiltration from abroad.
Reports suggest the pair are being held in a detention centre in Zhejiang.
They have not been allowed to see family members and personal effects, like computers, have been seized.
Bob Fu, China Aid president, said: "Arresting Pastor Wen and his family members for these meetings is a direct slap in the face to the U.S. government and the American people.
"He is a man with integrity and passion who is always ready to help others.
"Despite the constant threats state security agents posed to him and his family in the past few years, he and his wife have been boldly providing legal counsel for churches and persecuted human rights defenders in Zhejiang.
"I urge the U.S. government to work with the Chinese authorities for the immediate release of the Wen family and other innocent church leaders who are under arrest."
