SO Shiva..

[Mirron]

It's definitely an odd thing. And yeah, shapeshifting seems the most likely answer, assuming that the answer hasn't been distorted through the ages. Given the importance of Ishgard coming up and the rest, I imagine we'll get some answers soon enough.

[Sholah]

We know dragons can shapeshift into humans, as seen in the Coerthas section of the main story. But there are also smaller dragons she could have slept with, like a smaller wyvern, or the aevis type enemies.
Besides that, we don't even know if it's completely true. Remember that they're taking the history of Shiva from her archenemy.

[Morningstar1337]

We know dragons can shapeshift into humans, as seen in the Coerthas section of the main story. But there are also smaller dragons she could have slept with, like a smaller wyvern, or the aevis type enemies.
Besides that, we don't even know if it's completely true. Remember that they're taking the history of Shiva from her archenemy.

Indeed History is written by the winners.

This has me wondering if we'll find out more about Shiva soon enough.