What are step parents in French? My text says that 'step mother' and 'mother in law' are both 'la belle mère' but it seems like that could be rather confusing..
I confirm you that both "mother in law" and "step mother" mean belle-mère in French
Your belle-mère can be your father's new wife, or can be the mother of your husband/wife. In French we use the same word to express the both ideas.
That's the same regarding fathers -> beau-père means at the same time "step father" and "father in law"
Step parents are beaux-parents in French
But this simple rule isn't the same for all family members!
As in english, we have in French several ways to name our "step broters/sisters,..."
A step brother = Un demi-frère (is litterally a half-brother)
He's generally the son of your step mother/father
A brother in law = Un beau-frère
He's generally the husband of your sister, or your spouse/husband's brother
Moreover, to add some grammar details, be careful to the plural form of these words. As you maybe know you have in French plenty of exceptions...
demi-frère -> demi-frères (the word "demi" keeps its singular form)
demi-soeur -> demi-soeurs
BUT pay attention to:
belle-mère -> belles-mères (the word "belle" has to be declined to plural)
beau-père -> beaux-pères
Don't hesitate to comment for all additionnal information you may need :)
Hey, to add a small slang touch, do you know how to call a step mother or a mother in law in slang?
= une belle-doche ! or belledoche
And what about the brother in law?
= un beauf ! (short word for beau-frère)