Example 2. A woman and her brother, son, and daughter are all chess players. The twin of the worst player (also one of the four players) and the best player are of opposite sexes. The worst player and the best player are of the same age. Who is the best player?
If this woman is the worst chess player, then her brother must be her twin brother, and her daughter must be the best chess player, but the woman and her daughter cannot be the same age, so the assumption is not true.

If the brother is the worst chess player, then the woman must be his twin sister, and the best chess player would be the son. However, the woman and her son cannot be the same age. Therefore, the woman's twin brother cannot be the same age as her son.

If the daughter is the worst chess player, then the brother must be the woman's twin brother, and the best chess player would be the woman. But the woman and her daughter cannot be the same age.

If the son is the worst chess player, the daughter must be his twin sister, and the best chess player must be the brother. This is consistent with the known conditions, as the brother and the son can be the same age.
From the above reasoning, we know: the son is the worst chess player.