He doesn't know how it happened, or when it all started. You don't have the answer.
You can imagine that it all started in a fiery way, between fire and heat, which produced a fusion, without which she would never have come into existence.
But he doesn't remember.
Surely you have also deduced that little by little it was transformed.
They manipulated her into growing into what they had planned for her, and in the process, they always knew how far she could stretch and when to stop and release any pent-up tensions.
She has become aware of herself and has realized how they look at her.
She has understood that she transmits emotions, feelings and sensations that are not alien to her, and that she is unique.
It is a jewel, it is fusion.