The brother
In French, 'Le frère' is translated as 'The brother'. This word is used to refer to a male sibling. Unlike English, each noun in French has a gender, either masculine or feminine. 'Frère' is masculine so it's preceded by 'Le'.
Pierre's brother is tall.
This is a straightforward sentence showing the use of 'Le frère' which means 'The brother'. In this sentence, we are describing Pierre's brother as being tall. Note that the adjective 'grand' comes after the noun in French, which is reverse from English.
Anna's brother has two cats.
This example demonstrates the possession in French, signified by 'de' or 'd' before a vowel or a silent 'h'. Here, 'Le frère' means 'The brother', thus 'Le frère d'Anna' means 'Anna's brother'. The sentence says that Anna's brother has two cats.
Where is Marie's brother?
This is a question in French using 'Le frère'. Here 'Où est' translates to 'Where is' in English, 'le frère de Marie' translates to 'Marie's brother'. The sentence asks about the location of Marie's brother.