Ah no, that's not normal at all. Are you sure they weren't saying "Hon" (short for "Honey", a term of endearment)?

A son is always male in English. Perhaps it was "How many pancakes? Do you want some?" When making an offer, it's typical to use "some" instead of "any." Chinese speakers can mix up final M an N, and don't always pick up on English phrase level intonation.

Sorry, I'm not an English native speaker, but couldn't just disregard this funny story :) Maybe they mean 'sun'? Old ladies like to name people as 'sun', 'honey', 'sweetheart' and so on

A son is ones male offspring (child).

I'm quite sure she didn't think you were male , and she definitely wasn't calling you 'son' - 'son' is only for boys. I agree with the theory that what she said was actually: 'Do you want some?'. As Phil suggests, this wasn't exactly a question of your mishearing, but of failing to pick up on the intonation pattern and confusing 'm' with 'n' - both common issues with Chinese speakers.