At first glance, this family puzzle looks like a straightforward counting problem, but one small detail in the wording can easily lead you to the wrong answer. Mr. Wang and Mrs. Wang have three sons, giving us five people to begin with. Each son has one wife, adding three more people and bringing the total to eight.

The puzzle then says that every son has one son of his own. Since there are three original sons, that adds three children to the next generation, bringing the total to 11. At this point, many people may be tempted to choose 11, but there is still one important detail left to consider: every son has one sister.

The key is that the puzzle does not say each son has a different sister. The three brothers can all have the same sister. For example, Mr. and Mrs. Wang could have four children—three boys and one girl. Each boy would then have one sister, but that sister would be the same person for all three brothers. Therefore, we add only one sister rather than three.

Let’s check the total: two parents, three sons, three wives, three grandsons, and one sister. That gives us 2 + 3 + 3 + 3 + 1 = 12 people. The correct answer is therefore C. 12. The trick isn’t difficult mathematics; it’s understanding the relationships and making sure the same person isn’t counted multiple times. If you assumed that each brother had a different sister, you would get a different answer, but the wording never says that.