Astoria is the younger sister of Daphne Astoria and the little-known youngest daughter of the Greengrass family.
Greengrass is one of the oldest pure-blood families in the wizarding world. The last male heir was the sisters' father, Mr. Greengrass.
In Rowling's novels, Astoria is married to Draco Malfoy and has a son. But this does not satisfy our curiosity about her.
We can infer that her sister Daphne should be a clever witch, both of them are in the House of Snakes, and the family names come from Greek mythology.
What is the Greengrass family secret? What can a declining pure-blood family do to save its fate?