One's spouse's father. / (dated) A stepfather.

The sister of one's spouse. / The wife of one's sibling. / The wife of the sibling of one's spouse. / The sister of the spouse of one's sibling.

The brother of one's spouse. / The husband of one's sibling. / The husband of the sibling of one's spouse. / The brother of the spouse of one's sibling.

Husband or wife of one's cousin. / Cousin of one's husband or wife.

Someone's niece's husband / Someone's sibling's son-in-law / Someone's spouse's sibling's son-in-law / Someone's husband's nephew. (Usually called a nephew.)

Someone's nephew's wife. / Someone's sibling's daughter-in-law. / Someone's spouse's sibling's daughter-in-law. / Someone's husband's niece. (Usually called a niece.)

plural of mother-in-law

plural of father-in-law

plural of sister-in-law

plural of son-in-law