Naming the people you are related to, by blood and by marriage
My mother's brother is my uncle - my wife's brother is my brother-in-law
How to use this sheet
English names family connections in three layers, and each layer is built differently. The first covers the household you grow up in: a separate noun for each position, marked for sex, with a collective plural for the pair who raise you. The second reaches sideways, to the generation above you and to the children of that generation; one sex-marked pair covers the older line whichever side of the family it sits on, and a single common-gender noun covers the younger. The third layer is not inherited but acquired: marriage attaches a fixed tail to a word you already know, while a remarriage in the household attaches a short prefix to the front of another.
| Person | Relationship | Note |
|---|---|---|
| parents | your mother and father together | Almost always plural in this sense; one of the two on their own is a parent. |
| sibling | a brother or a sister, of either sex | Formal and mostly written; in speech people name the person as a brother or a sister. |
| grandmother, grandfather | the mother or father of one of your parents | Add great- for each further step back: great-grandmother, great-great-grandfather. |
| aunt, uncle | the sister or brother of one of your parents | One pair of words covers both sides; English has no separate maternal and paternal terms. |
| cousin | the child of your aunt or uncle | The same form for male and female, and a regular plural: my two cousins. |
| niece, nephew | the daughter or son of your brother or sister | Niece is female and nephew is male; there is no single word covering both. |
| mother-in-law | the mother of your husband or wife | The plural goes on the head noun: two mothers-in-law, never two mother-in-laws. |
| brother-in-law | the brother of your husband or wife, or the husband of your sister | One word for two different relationships; the plural is brothers-in-law. |
| stepmother | the woman your father married after your mother | Written as one word with no hyphen, and pluralised at the end: stepmothers. |
| stepbrother | the son of a step-parent, sharing no parent with you | No blood connection at all, which is what separates it from the next row. |
| half-brother, half-sister | a brother or sister who shares one parent with you | Half- signals one shared parent; step- signals none. Both take a hyphen here. |
| spouse | the person you are married to | Formal and neutral for either sex; partner is the everyday word and states nothing about marriage. |
| relatives | everyone connected to you by blood or by marriage | Also called relations; the whole group beyond the household is your extended family. |
In use
My mother's brother is my uncle, and his daughter is my cousin. I get on well with both of my brothers-in-law and with my mother-in-law. After my father remarried I gained a stepmother and, two years later, a half-sister.
Watch out
The sister of my father is my aunt, and my two brother-in-laws live nearby.
Two habits carried over from other languages collide in the incorrect sentence. The opening phrase builds the relation with a preposition, as most European languages do. English allows that preposition elsewhere, but for family terms it strongly prefers the possessive ending, placed on the person who holds the relation and put first, so the order reverses and the linking word drops out. The second half then pluralises the compound at the very end; a compound whose second half is a fixed prepositional tail keeps its plural on the head noun at the front, where the meaning sits. The prefixed forms behave differently again: nothing follows their head noun, whether written solid or with a hyphen, so their plural does go on the end.