"All of his ribs are fractured," Mieses' mother, Yolanda Santiago, told WBZ, "his lungs are so badly bruised that he's still on a ventilator."
Mieses' wife said he had been trying to help the first biker who was initially hit by the SUV when he, too, was hit.
His family has said he is paralyzed and in a coma.
Police said the biker group, called "Hollywood Stuntz," chased the driver, whose flat tires forced him to stop.
Cornered, Lien was beaten, police said. He was treated at a hospital for slashes to his face and released. Neither his wife nor his child was hurt.