The Duke of York and the Earl of Wessex have been made Royal Knights of the Garter by the Queen.
Princes Andrew and Edward were both appointed to the most senior British order of chivalry on St George's Day amid a weekend of celebrations to mark the Queen's 80th birthday.
It recognises their seniority within the Royal Family.
The Order of the Garter, established by Edward III in 1348, is in the Queen's personal gift, without advice from government ministers.
Knights of the Garter are chosen to honour those who have held public office, who have contributed to national life or who have served the Sovereign personally.
The Duke and the Earl, the Queen's middle and youngest sons, are now Royal Knight Companions.
Their appointments are additional to the established number of 24 Knight Companions.
The two royals now join their father the Duke of Edinburgh, brother the Prince of Wales and sister Princess Royal in the Order.
Philip was created a Royal Knight in 1947 - the year he married Princess Elizabeth.
Charles became a Knight in 1958 on his creation as Prince of Wales, the Duke of Kent in 1985, Anne in 1994, the Duke of Gloucester in 1997 and Princess Alexandra in 2003. The non-royal members of the Order include former Prime Ministers Baroness Thatcher and Sir John Major.