British Citizenship Test 2025 – All-in-One Study Guide to Pass with Confidence!

The heir to the British throne is the monarch's oldest son. In this case, that refers to King Charles III, whose son, Prince William, is second in line to the throne. The line of succession typically follows the direct descendants of the reigning monarch, starting with the eldest son.

The title of heir apparent is given to the first-born child of the monarch until they pass away or are displaced by a closer relative. In the context of this question, since the Queen was Elizabeth II until her passing in September 2022, her oldest son, Charles, holds the status of heir to the throne. The other options relate to family members who are either further down the line of succession or do not hold the title of heir. For example, the Queen’s youngest son would not be the primary heir, the Queen's brother was not in line for the throne following the establishment of primogeniture, and her grandson would follow his parent (the eldest son) in the line of succession.