Ashraf Azad, 28, could face jail time at his sentencing on Jan. 21 for assaulting Afshan Azad, 22, who played Harry's classmate Padma Patil in the films, the BBC reports.
However, Ashraf and his father, Abdul Azad, were cleared of charges that they threatened to kill the young actress.
The young actress's family, who are Muslim, did not approve of her relationship with a Hindu man, according to prosecutors.
The assault took place at the family's home in Manchester last May. Afshan reportedly fled through her bedroom window to escape her brother, and later accused him and her father of threatening her life.