Yu-Gi-Oh! episode 87: "Awakening of Evil, Part 2"
Mrs. Ishtar married into the Ishtar family and became a grave keeper of the Tomb of the Nameless Pharaoh. One night, she found a nameless infant boy, who was abandoned by his biological parents. Mrs. Ishtar adopted him and named him Odion (Rishid in the Japanese version), and treated him as a real son. Her husband, however, refused to accept the boy as anything more than a servant.
As Odion grew, the couple became increasingly desperate to have a male child as the heir to the tomb-keeper clan. Mrs. Ishtar proposed that they should have Odion initiated if they do not have a boy by his tenth birthday (twelfth in the English anime), to which her husband reluctantly agreed. When Odion was six years old, Ishizu was born; Mr. Ishtar showed displeasure after her birth about still not having a male biological child. Four years after that, the Ishtars finally had a boy, Marik, to which Mrs. Ishtar died during childbirth. Her last words to Odion and Ishizu was for them to take care of each other.