More than 130 attorneys and legal staff were summoned in July for questioning in what campaigners call the fiercest attempt yet to silence activists attempting to redress injustices in China's tightly controlled courts.
Wang Yu, of Beijing's Fengrui law firm which is at the centre of the crackdown, has been formally arrested on suspicion of "state subversion", which carries a maximum sentence of life in jail, her lawyer Li Yuhan told AFP.
It is the first time the couple's family have been notified of their whereabouts, more than six months after they were detained.
Their son, Bao Zhuoxuan, 16 is also being held under a form of house arrest, friends say. The teenager was nabbed in October after crossing overland to neighbouring Myanmar, according to state-run media.
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Over the past decade a small group of a few hundred Chinese lawyers attempted to use the court system to seek redress -- sometimes successfully -- for what they considered egregious rights violations.
State media -- which in the past sometimes praised rights lawyers' efforts -- have called the attorneys a "criminal gang" who created public disorder by organising protests outside courthouses to illegally sway verdicts.
China's ruling Communist Party does not tolerate organised dissent and has tightened controls on civil society under the leadership of President Xi Jinping.
Wang Yu is best known for defending Uighur intellectual Ilham Tohti, as well as alleged victims of forced demolition and sexual assault.
It has also shown Wang and her husband breaking down in tears on hearing the news of their son's capture.