We all have families—even aliens do—but sometimes we don’t know which word to use for particular members, especially those who are not part of our immediate family.
Just to be sure, these are the words in family vocabulary you might wish to know:
Nuclear family: consists of father, mother and their child/children.
Extended family: the nuclear family and families of both parents all together.
Monogamy: the practice of being married to one person at a time.
Polygamy: the practice of being married to more than one person at the same time.
Bigamy: the crime of marrying another person while still married to one.
Blood relation: related by blood rather than through marriage.
Relatives: people connected by blood or marriage.
Spouse: your husband or your wife.
Paternal: of your father (e.g. paternal grandfather).
Maternal: of your mother (e.g. maternal grandparents).

Great-grandfather: the father of your grandfather or grandmother.
Great-grandmother: the mother of your grandfather or grandmother.
*Both are called great-grandparents.
Grandfather: the father of your father or mother.
Grandmother: the mother of your father or mother.
*Both are called grandparents.
Grandson: the son of your son or daughter.
Granddaughter: the daughter of your son or daughter.
*Both are called grandchildren.
Father: your male parent.
Mother: your female parent.
*Both are called parents.
Brother: the male child of your parents.
Sister: the female child of your parents.
*Both are called siblings.
Son: your male child.
Daughter: your female child.
*Both are called children.
stepfather: the husband of your mother who is not your biological father.
stepmother: the wife of your father who is not your biological mother.
*Each of them is a step-parent(UK); step parent(UK); stepparent(US).
stepbrother: the son of your stepfather or stepmother.
stepsister: the daughter of your stepfather or stepmother.
*Both are step-siblings (UK); step siblings (UK); stepsiblings (US).
Stepson: the son of your husband or wife from another marriage.
Stepdaughter: the daughter of your wife or husband from another marriage.
*Both are called stepchildren.
Half-brother: a brother who shares only one of your parents with you.
Half-sister: a sister who shares only one of your parents with you.
See: Simplified difference between stepbrother/stepsister and half-brother/half-sister
Father-in-law: the father of your husband or wife.
Mother-in-law: the mother of your husband or wife.
*Both are called parents-in-law.
Son-in-law: the husband of your daughter.
Daughter-in-law: the wife of your son.
Brother-in-law: the brother of your wife or husband; the husband of your sister; the man who is married to the sister of your wife or husband.
Sister-in-law: the sister of your wife or husband; the wife of your brother; the woman who is married to the brother of your wife or husband.
*Plural forms: sons-in-law, daughters-in-law, brothers-in-law, sisters-in-law; all are in-laws.
Uncle: the brother of your father or mother; the husband of your aunt.
Aunt: the sister of your father or mother; the wife of your uncle.
Cousin (also first cousin) : the child of your uncle or aunt; more generally, a distant relation.
First cousin once removed: the child of your first cousin; your parent’s first cousin. Basically, there is a generation between you and your ‘first cousin once removed’, i.e. you are separated by your first cousin, hence the concept of ‘once removed’ (see analysis here)
Second cousin: the child of your first cousin once removed; the child of your parent’s first cousin.
Nephew: the son of your brother or sister; the son of your wife or husband’s brother or sister (brother-in-law or sister-in-law).
Niece: your brother or sister’s daughter; the daughter of your wife or husband’s brother or sister (brother-in-law or sister-in-law).
Wow! Interesting and detailed but What do you mean by first cousin once removed?
Thank you. First cousin once removed is the child of your first cousin.’Removed’ simply means that one generation is removed or that you are separated by one generation (your first cousin). Do you understand, ma?
What is the son of a step brother called
Step-nephew. Some might prefer just ‘nephew’ to erase the ‘step’ barrier.
Thank you very much for this .
What is the brother of ur stepmom called?
Legally, you don’t have any relationship with your stepmom. You can call his brother your uncle, but it’s just courtesy.
What is my half brother sister children to me
They are referred to as half-niece (female) and half-nephew (male). Though this is not common in English and some speakers believe the words do not exist, they do exist.