die Schwester
sister
A female person who has the same parents as another person.
Meine Schwester und ich verstehen uns sehr gut.
My sister and I get along very well.

sister
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sister
A female person who has the same parents as another person.
Meine Schwester und ich verstehen uns sehr gut.
My sister and I get along very well.

The context shows which 'Schwester' (sister/nurse/nun) is meant. Words like 'Eltern' (parents) or 'Bruder' (brother) point to family. A medical setting ('Krankenhaus' (hospital), 'Arzt' (doctor)) refers to a nurse. Religious terms like 'Kloster' (monastery/convent) or 'Orden' (religious order) signal a nun.
Meine jüngere Schwester studiert Medizin.
My younger sister is studying medicine.
In a hospital or doctor's office, it is common to address a female nurse directly as 'Schwester' (nurse), often without knowing her name.
Schwester, könnten Sie mir bitte ein Glas Wasser bringen?
Nurse, could you please bring me a glass of water?
With nuns, 'Schwester' (Sister) is used like a title, normally followed by the person's first name. It is a respectful form of address.
Schwester Johanna leitet den Kindergarten des Ordens.
Sister Johanna runs the order's kindergarten.
brother
'der Bruder' and 'die Schwester' both belong to the topic of family and refer to a sibling. The difference is gender: a brother is male, a sister is female. The words can be confused because both describe the same family relationship. If you only want to say that someone is not an only child, you often need 'Geschwister' (siblings). If gender is important, you say 'Bruder' or 'Schwester'.

Nach dem Gespräch hat die Mitarbeiterin ihre Schwester angerufen.
After the conversation, the employee called her sister.
Mein Bruder hilft mir heute beim Umzug.
My brother is helping me move today.