The Queen has a huge family - but her relationship with her grandaughters-in-law Catherine and Meghan has always been the subject of much speculation.
As the wives of two of her closest heirs to the throne, the monarch occasionally heads on official engagements with the Duchess's - and one day, Catherine will take on her role as Queen, albeit Queen Consort.
But according to one royal biographer, Ingrid Seward, she has a very different relationship with the two ladies, for a very good reason.
Ingrid, who is editor-in-chief of Majesty Magazine, revealed that while Catherine and the Queen have a more serious, formal relationship, she has a more relaxed one with Meghan.
She explained, “The Queen admires Kate tremendously but does not have an intimate relationship with her as they don’t have much in common. I think the Queen and Kate have a more serious relationship as obviously Kate holds all the Queen’s hope for the future and she would not want to do anything to upset that.
“The common bond with Kate would be her children and I can’t imagine the Queen spending too much time talking about them; she is a very shy woman, which is why a common subject like horses is so helpful.”
It seems that Meghan's love of dog may have helped her to bond with the Queen, and given them an easy topic to discuss as they got to know each other.
Ingrid continued, “With Meghan she would tread very carefully and do her best to make her feel at home. They have a love of dogs in common and Meghan knows how to make her laugh.”
Of course, Prince Harry and Meghan Markle themselves revealed that the Queen's dogs instantly took a liking to her when she first met the monarch. Harry explained, "And the corgis took to you straight away. I've spent 33 years being barked at, this one walks in and nothing."
Before Meghan laughed saying, "Yes, just laying on my feet. It was very sweet."
The comments certainly make sense - eventually, Kate will be stepping in to the Queen's footsteps, explaining the need for a more professional and formal relationship.
It's highly likely Meghan will never be in Catherine's postion, suggesting why the monarch can take a more relaxed approach with Harry's wife.