The decision to release the prisoners is seen as a signal to neighboring Afghanistan that Pakistan might be willing to take concrete steps to revive efforts to lure the group to the negotiating table.
Pakistan released Anwarul Haq Mujahid on Thursday, and he joined his family in the northwestern Pakistani city of Peshawar, said the cousin and family friend, speaking on condition of anonymity because they were not authorized to talk to the media.
Mujahid is the son of the late Maulvi Mohammad Yunus Khalis who fought against the Soviets in Afghanistan in the 1980s. Khalis, who was once invited to the White House by former President Ronald Regan, died in 2006.
Afghan officials said Thursday that Pakistan freed eight Taliban prisoners and agreed to release many more. Mujahid was not among the eight listed by the Afghan officials, which means at least nine prisoners have been freed.
The most prominent prisoner freed was former Justice Minister Nooruddin Turabi who served when the Taliban ruled Afghanistan.
The U.S. and its allies fighting in Afghanistan are pushing to strike a peace deal with the Taliban so they can withdraw most of their troops by the end of 2014. The prisoner release could help, but considerable obstacles remain. It is unclear whether the Taliban even intend to take part in the process, rather than just wait until foreign forces withdraw.
Pakistan is seen as key to the peace process. Islamabad has ties to the Taliban that date back to the 1990s, and many of the group's leaders are believed to be based on Pakistani territory, having fled there following the U.S.-led invasion of Afghanistan in 2001.
Also Friday, a Pakistani lawyer accused the military of sending thugs to beat him up after he challenged the army chief in court.
Inam Ur Raheem, a retired military lawyer, said three vehicles surrounded his taxi Wednesday night in the garrison city of Rawalpindi. Several unidentified men jumped out and attacked him with sticks, leaving him with cuts and bruises. He claimed they said they were there to teach him a lesson.
The attack came a day after Raheem filed a petition in the Islamabad High Court challenging the validity of a three-year extension given to army chief Gen. Ashfaq Parvez Kayani in 2010.
The army denied any role in the attack Friday, calling Raheem's allegations baseless.
The New York Times first reported the attack Thursday.
Associated Press writer Munir Ahmed contributed to this report from Islamabad.