FOR Pakistan Prime Minister Benazir Bhutto, family feud and political rivalry overlapped in a cruel twist on September 20 when her estranged brother Murtaza was killed in a shootout with the police near his 70 Clifton residence in Karachi. Adding to her woes is the speculation that her husband Asif Zardari scripted this latest chapter in the violent Bhutto saga. And, as has happened all too often in Pakistan, personal tragedy for the Bhuttos is turning into political nightmare for Pakistan as uncertainty looms large over the future of its prime minister. As the Jang newspaper observed: "Benazir is facing a most trying moment of her life."