The other hunger striker, Salim Masar, is in his late 30s and a laborer, has not been charged, the attorney said.
Zubeidi announced on Sunday he would refuse all food and liquid until he is released from Palestinian Authority custody, after almost four months in jail without charge.
The director of Jenin refugee camp’s Freedom Theater, which Zubeidi co-founded, said staff are very concerned as people only survive without fluids for around a week.
“He has really had enough of being kept in jail with no charges,” Jonathan Stanczak said.
Zubeidi was detained on May 13 and his detention has been repeatedly renewed without charges being pressed. At a court hearing on Sunday his detention was renewed for another eight days.
A week earlier, at another renewal hearing, the judge had persuaded Zubeidi to delay his hunger strike while they gathered more information.