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.

(law) The body of law dealing with the private relations between members of a community; it contrasts with criminal law, military law and ecclesiastical law.

(law) The area of law pertaining to crime and punishment. / (law) A specific statute, ordinance, regulation, or other source of law that deems an action to be a crime.

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.)

(Britain, law) A former (1824–1981) law by which police officers were permitted to arrest anyone under suspicion of having committed a crime

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.)

(chiefly UK) The principle that what can go wrong, will go wrong, usually with some observed degree of irony