Angelina Jolie may have to buy off Pax's mom

Angelina Jolie's adopted son Pax Thien was the child of a drug addict, it has been claimed. Heroin-addict Pham Thu Dung reportedly abandoned her son when he was just two days old, and fears are growing she may demand he returns to Vietnam. Angelina - who adopted Pax last week - is said to be worried Dung, 29, could hound her for money or threaten to contest the adoption because the adoption papers were only signed by the tot's grandparents. Pax's grand dad Chien told Britain's News of the World newspaper: "Our daughter is a heroin addict and her life has been ruled by drugs. When she finds out a rich movie star has adopted her baby, she will go after her for money and make trouble. She may even try to take the child back."Chien revealed Dung became pregnant following an affair with a married man and gave birth to a dangerously underweight son. Doctors even feared the baby would be born a heroin addict. Dung abandoned Pax as he lay critically ill in hospital because she couldn't afford the $30. medical bill. Pax was sent to Ho Chi Minh City's Tam Binh orphanage and hasn't seen his mother or grandparents since. Chien added: "We never visited Pax because we were scared we would fall in love with him and I knew we couldn't afford to keep him."Dung was at our house when we heard a wealthy American wanted to adopt Pax. She showed no emotion. Then she disappeared - she was still hooked on drugs.We signed the adoption papers and said we didn't know where our daughter was."Dung's sister Trang believes she is desperate to see Pax again. She insisted: "My sister thinks about her baby a lot. If she could, she would try to get her son back."Pax is Angelina's third adopted child - she already has five-year-old Cambodian son Maddox and two-year-old Ethiopian daughter Zahara. Angelina and lover Brad Pitt also have a 10-month-old daughter Shiloh together.