Question

can a king make his sister the heir even if he has a queen?

Answer 1

In most monarchies, the line of succession is determined by strict rules and traditions, often based on primogeniture or other established criteria. It would be highly unusual for a king to bypass his queen and name his sister as the heir to the throne. However, monarchs have the authority to change the line of succession through official decrees or legislation, so technically it is possible for a king to make his sister the heir if he chooses to do so. Ultimately, the decision would depend on the specific laws and customs of the particular monarchy in question.