The brother
In Italian, 'Il fratello' translates directly to 'The brother' in English. It is used to refer to a male sibling. Just like in English, it can be used to relate familial relationships, or metaphorically to describe close bonds. Note that, in Italian, every noun is assigned a gender and number, and the article 'il' is used for singular masculine nouns.
Maria's brother studies medicine.
In this sentence, 'Il fratello di Maria' refers to Maria's brother who is studying medicine. 'Studia' is the third person singular present tense of the Italian verb 'studiare', which means 'to study'. 'Medicina' is the Italian word for medicine.
Luigi's younger brother is a famous lawyer.
In this example, 'Il fratello più giovane di Luigi' refers to Luigi's younger brother who is a renowned lawyer. 'Più giovane' means 'younger', 'è' is the third person singular of the verb 'essere' which means 'is', and 'un avvocato famoso' means 'a famous lawyer'.
I met Paolo's brother at the market yesterday.
This example 'Ho incontrato il fratello di Paolo al mercato ieri' translates to meeting Paolo's brother at the market yesterday. 'Ho incontrato' is the first person singular past tense of the verb 'incontrare', which means 'to meet'. 'Al mercato' means 'at the market', and 'ieri' means 'yesterday'.