Why is this the answer?

The answer is sister because this is a very clever word puzzle that tries to trick your brain with the first few words. The secret is to slow down and think about exactly what each part of the riddle is saying. Let's look closely at the two main clues it gives us. The first clue says, "A beggar's brother went out to sea and drowned." This fact tells you that the beggar is a person who has a brother. You can picture the beggar in your mind, and you know this beggar has a male sibling. The person who drowned is this beggar's brother. Now, here comes the sneaky part, the second clue: "But the man who drowned had no brother." This is the key to solving the riddle. The drowned man cannot have a brother. If the drowned man cannot have a brother, and the beggar is the only sibling mentioned, the beggar must be his sister. Think about it like this. The man who drowned is the one whose siblings we are counting. He has no brothers, but he must have the beggar as a sibling because the beggar's brother is the drowned man. The only other kind of sibling he can have is a sister. Therefore, the beggar must be the drowned man's sister. If the beggar is the man's sister, it still fits the first clue perfectly. A sister has a brother, and that brother is the one who drowned at sea. The riddle only says the beggar has a brother who drowned, which is true. It never said the beggar was a boy. This simple change in your thinking unlocks the whole puzzle and proves why the answer is sister. It is a fantastic trick riddle that makes you guess a boy's relationship when the person is a girl.