Why is Saudi Arabia the Crown Prince?

Not all Saudis are crown princes. The Saudi prince is actually a descendant of the old Saudi king Ibn Saud. Saudi Arabia is also called Saudi Arabia, because the old king Ibn Saud has the word Saudi Arabia in his name. The Saudi Crown Prince is the heir to the Saudi king, and there can only be one Saudi king. In the past, it was inherited by brothers and sisters, that is, brothers inherited the throne first. In recent years, the current king has broken the rules. At first, he made his nephew a crown prince, and now he makes his son a crown prince. The relationship between the Saudi Crown Prince and the Prince is that the Crown Prince is also a prince, but this Crown Prince is used to inherit the throne.