Can more than one person have the same devil fruit power? How come in the island Amazon Lily, the snake princess's sisters have the same devil fruit power?

Since only one person can have any given devil fruit power at a time, does it have to do with blood line or something?
They have similar fruits but not the same.
Boa Marigold has the Hebi Hebi no Mi, Model: King Cobra.
Boa Sandersonia has the Hebi Hebi no Mi, Model: Anaconda.


  A majority of the Zoan Devil Fruits also come in different "models" that result in variations of the animal. For example, the Inu Inu (Dog) Fruit has Jackal, Dachshund, and Wolf models, the Ushi Ushi (Bull or Cow) Fruit has Bison and Giraffe models, and the Hebi Hebi (snake) has Anaconda and King Cobra models.  


Source