Could it be that...
Eboshi was actually San's mother? There are IMO multiple things in the film that would support this theory:
- Moro says San was abandoned by the humans as a baby
- Eboshi says San exists to kill her, and seems to hold a particular hatred for her
- Judging by her looks, I'd say Eboshi looks about 35-40 years of age, which would suit the high status she's achieved. I wouldn't see a younger woman being in such a high position as she is.
- San would seem to be about 16-18 years old. Considering the time period, it wouldn't be implausible at all that Eboshi could have had a child when she was 16-20 years old.
Do you think this theory holds up? I think there's some implied undertone in the film towards this, and I want to know if others think the same.