"My stepfather is my mother's husband."
Translation:Mon beau-père est le mari de ma mère.
When this issue came up only "father-in-law" was listed as correct, both in the prompts and in the actual answer. Should I report it the next time? Same thing goes for "C'est mon beau-frère" was translated only as "brother-in-law" "C'est ma belle-mère" as "mother-in-law" and "C'est ma belle-sœur" as "sister-in-law." "Step-brother" was listed for "demi-frère" but "half-brother" (sharing one parent) was not.
Your question was about "c'est mon beau-père", who indeed can be my father-in-law or my stepfather.
In the sentence here, a precise context is set: "my mother's husband" is necessarily "my stepfather", otherwise, his description would be "my husband/wife's father".
"Mon beau-frère" can be my wife's brother, my husband's brother or my sister's husband depending who I am.
But he can't be my stepbrother or half-brother: "mon demi-frère".
"Ma belle-soeur" (sister-in-law) can be my husband's sister, my wife's sister or my brother's wife.
"Ma belle-mère" is my father's wife (stepmother) or my husband's mother (mother-in-law)
"Ma demi-soeur" is my stepmother's/stepfather's daughter (step sister) or we share one parent, mother or father (half-sister)..