Theorie:

In order to speak about a family, you should know the proper vocabulary. 
  
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Relatives - members of a family

Grandfather - the father of a person’s mother or father

Grandmother - the mother of a person’s mother or father

Aunt - the sister of your mother or father, or the wife of your uncle

Uncle - the brother of your mother or father, or the husband of your aunt

Cousin - the child of your aunt and uncle

Father-in-law - the father of someone’s husband or wife

Mother-in-law - the mother of someone’s husband or wife

Brother-in-law - the husband of your sister or brother, or the brother of your husband or wife

Sister-in-law - the wife of your brother or sister, or the sister of your husband or wife

Nephew - a son of your sister or brother, or a son of the sister or brother of your husband or wife

Niece - a daughter of your brother or sister , or a daughter of your husband’s or wife’s brother or sister

Widower - a man whose wife has died and who has not married again

Widow - a woman whose husband has died and who has not married again

Stepfather - the man who is married to someone’s mother but who is not their real father

Stepmother - the woman who is married to someone’s father but who is not their real mother

Godfather - a male godparent

Godmother - a female godparent

Single-parent family - a family with one parent (a mother or a father)
Quellen:
http://dictionary.cambridge.org