The gala event honoured Charles' service to the Welsh region and was attended by Her Majesty Queen Elizabeth, the Duchess of Cornwall, the Duke and Duchess of Cambridge, the Duke and Duchess of Sussex and Anne, Princess Royal.
But while Charles' little sister was on hand to celebrate the occasion, his younger brothers were nowhere to be seen.
As reported by Royal Central, Prince Andrew, Duke of York and Prince Edward, Earl of Wessex were notable absentees from the festivities.
According to the publication a possible reason for the Prince's absence may be because Princess Anne played a active part in the investiture ceremony half a century ago while they did not.
The Princess Royal, then 18, was present at Wales' Caernarfon Castle in 1969 while Andrew, aged 9 and Edward, just five-years-old, were too young to attend.
Other possible explanations may be that the brother's had prior commitments, with the Court Circular noting the Earl of Wessex was at St James' Palace for a series of meetings on Tuesday as part of his role as Trustee of The Duke of Edinburgh's Award.
Royal fan watchers were sent into overdrive as the celebrations unfolded as the event marked the first time Kate Middleton and Meghan Markle have appeared in public together since Christmas Day.
The wives of Windsor dressed to impress in their own unique styles, with Duchess Catherine wearing a timeless powder blue button front dress reportedly created by a private seamstress, per Harper's Bazaar.
WATCH: Meghan and Kate reunite for Prince Charles' celebration
Kate paired the look with a pair of white pointed toe stilettos.
Heavily pregnant Meghan, who is due to give birth to the Sussexes' first child in April, opted for a gold brocade dress with a white coat by Amanda Wakeley and her trademark nude pointed court heels.