Last week the monarch celebrated her 94th birthday while in isolation at Windsor Castle with her husband Prince Phillip.
The current lockdown restrictions prevented her majesty from seeing extended family on the special occasion, and two people, in particular, were left extremely “sad” according to royal author Leslie Carroll.
Ms Caroll told Express.co.uk: “Both William and Kate are very close to their respective families, so it must be extremely difficult for them not to see them, and for their children not to be able to spend time with them as well.
“They were unable to share Her Majesty’s 94th birthday with her in person; so that must have been somewhat sad for everyone. “
The Queen did not want to publicly celebrate her birthday during this unprecedented time, as she enjoyed a very low key day at home.
She had several video calls with family members, including the Sussexes who shared the footage with their media outlets.
A spokesperson had previously said: “Her Majesty’s birthday will not be marked in a special way – and calls, video calls, with family will be private and kept so.
“There will be no gun salutes. Her Majesty was keen that no special measures were put in place… as she did not feel it was appropriate in the current circumstances.”
On social media, Kate and William posted a sweet photo tribute of the Queen and wished her many happy returns.
Buckingham Palace thanked the public for their kind wishes and shared private footage of the Queen as a young princess.
The Royal Family’s Twitter account added: “To those of you also celebrating your birthdays today at home, with or without your loved ones – we send you many happy returns.”
It has also been reported that the Duke and Duchess of Cambridge feel concerned for Kate’s parent’s health during this unprecedented time, as lockdown has kept her from visiting them.
Leslie Carroll revealed: No doubt they are very concerned about the health and wellbeing of Carole and Michael Middleton and of the most senior royals.
“But the Cambridges also convey a great deal of diligence and responsibility and attention to duty-everything one expects from future monarchs.
“Therefore I doubt that they would consider breaking, or even bending, any of the NHS advisories that would jeopardise their family’s health (not to mention what a dreadful optic this would be for the nation and Commonwealth).”
It comes as the couple set up a mental health support service to help frontline workers through their Royal Foundation charity.
Kate and William launched Our Frontline as they feared the strain placed upon NHS workers, carers and emergency service staff.
The new phone line was set up alongside Samaritans, Mind, Shout and Hospice UK providing access to specially developed online resources.
“Over the past few weeks, millions of frontline workers across the UK have put their physical and mental health on the line to protect us all during the Coronavirus pandemic,” Prince William said.
“Every day they confront traumatic situations at the same time as having to contend with their own worries about the risks to themselves and their families.
“That takes a real toll, and as I’ve seen for myself through my work with the Air Ambulance, without the right support at the right time the challenges they face will only be greater.
“Catherine and I, together with The Royal Foundation, will do all we can to support Our Frontline. This work will be our top priority for the months ahead.”