Use a hyphen to link a relationship term: sister-in-law, mother-in-law, father-in-law, brother-in-law, ... Plurals: sisters-in-law, brothers-in-law, mothers-in-law… But: stepmother, stepfather, stepdaughter, stepson, stepchild.

Is step brother one word or two words?

Word forms: stepbrothers

Someone's stepbrother is the son of their stepfather or stepmother.

Does step by step have hyphens?

When a compound adjective comes before a noun, hyphenate it: step-by-step instructions. If the adjectives follow the noun, do not hyphenate them: the instructions were step by step.