At first glance, this family puzzle looks like a straightforward counting exercise. Mr. and Mrs. Wang have three sons, giving us five people. Each son has one wife, adding three more people and bringing the total to eight. Then, each son has one son, adding three children and bringing the count to 11.

But the final detail changes the answer. The puzzle says that every son has one sister. It does not say that each brother has a different sister. The three brothers can all share the same sister, just as siblings in a real family can have one sister in common.

To avoid counting anyone twice, we can list the family members individually: two parents, three sons, three wives, three grandsons, and one sister. That gives us 12 people in total. The sister is part of the same generation as the three brothers, while the three younger boys are their children.

This is what makes the puzzle tricky. An answer of 11 leaves out the sister, while adding three sisters would incorrectly assume that each brother has a different one. The wording gives us no reason to make that assumption, so the three brothers can have the same sister.

Therefore, the answer is 12 people. The puzzle is less about complicated mathematics and more about reading carefully. Sometimes a single word or relationship can change the entire calculation, which is why it helps to identify each individual person before adding up the total.