Paŝo-patrino vs. paŝopatrino.
Is there a difference in the meaning of the word if I add a hyphen? I am trying to say step-mother (paŝo-patrino), rather than mother-in-law (paŝopatrino)
I'm not sure if that is grammatically sound or not.
I think you can use hyphens to clarify compounds, but this is not done often. In the early day of Esperanto, apostrophes were used to seperate the building blocks of words, but this was abandoned rapidly, since it is cumbersome and in my eyes a bit ugly. I think cases were there are several possibilieties to deconstruct a word (like kat'okul'o cat eye and kat'o'kul'o cat-like gnat) are very few and context should help there.
It isn't a mother-in-law a "bopatrino" and a stepmother a "vicpatrino" or "duonpatrino"?
This is correct. When talking about family words:
- bo- = in-law
- duon- = step-, half-
- vic- = step-