The King is reportedly planning to make changes to the law to prevent non-working royals being counsellors of state.
Under the new plans, Prince Andrew, Prince Harry and Princess Beatrice would all become ineligible to stand in for the monarch.
The 1937 Regency Act dictates that the spouse of a monarch and the four adults next in line to the throne can act as counsellors of state.
Counsellors can fill in for the monarch, should they be indisposed.
During the latter years of the Queen's reign, the roles were filled by the Prince of Wales, the Duke of Cambridge, the Duke of Sussex, and the Duke of York, as well as the Duke of Edinburgh before his death.
The ascension of King Charles means Queen Consort Camilla, as the King's spouse, and Princess Beatrice, as the next adult in line to the throne, are eligible to become counsellors of state.
However, that would leave three of the five counsellors as non-working royals in Prince Andrew, Prince Harry and Princess Beatrice.
The Telegraph reports that it is believed that the King recognises the incongruity of having a trio of non-working Royals eligible to fill in should he be abroad or incapacitated.
The King is believed to be keen to take the relevant steps to have the law changed as soon as possible, with his siblings the Earl of Wessex and the Princess Royal likely candidates to fill two of the positions.
There could also be a wider reformation that would attempt to clearly define the position of working and non-working royals.
Should the new requirements not focus solely on the line of succession, it is possible the Princess of Wales could be included.
Counsellors of state are rarely called upon, although they have occasionally been required in recent years.
Prince Charles and Prince William attended the state opening of Parliament in May as they deputised for the Queen, with two counsellors required to be present in order to be constitutionally sound.
Parliament would have to pass any change in legislation.
In 1953, the Queen requested that a provision be added ensuring that if a child of the Queen and Duke of Edinburgh acceded to the throne before turning 18, Prince Philip would become Regent.
