Learn Turkish: Benim bir erkek kardeşim var.

Turkish doesn't have a direct verb for "to have". Instead, you express possession by saying "my [thing] exists". Here, Benim means "my" and var means "there is" or "exists". So literally, this sentence is saying "My one male sibling exists."

Why does kardeş have the -im suffix if we already used Benim (my) at the start?

In Turkish, you must attach a possessive suffix to the thing being owned. The -im in kardeşim is the 1st person singular possessive suffix showing that the brother belongs to "me". Using Benim at the start is actually optional and just adds emphasis, but adding -im to the noun is strictly required!

Why do we use two words, erkek kardeşim, to say "brother"?

The word kardeş just means "sibling" and doesn't specify a gender. To specifically say "brother", you add erkek (male) in front of it. Notice that the possessive suffix -im only attaches to the final noun kardeş, making it erkek kardeşim.

Why is bir placed after Benim?

Bir means "a" or "one", and in Turkish, it usually goes directly before the noun it describes. Since it describes the brother, it is placed right in front of erkek kardeşim rather than at the very beginning of the sentence.