Since Prince Charles stepped in at the 11th hour to walk Meghan Markle down the aisle on her wedding day, their bond has only continued to grow.
From their close display at Prince Charles' garden party, to reports the American actress has brought Prince Harry closer to his father, Meghan and Charles are clearly very fond of each other.
And now, Prince Charles' nickname for Meghan Markle has been revealed and it's just adorable.
According to the Daily Mail, the 69-year-old has been so impressed with his daughter-in-law that he's started to call her "Tungsten" after the rare metal because she's "tough and unbending just like the very strong metal."
Indeed, the scrutiny Meghan Markle has faced would be enough to upend almost anyone but the Duchess of Sussex has taken it all in her stride.
"Prince Charles admires Meghan for her strength and the backbone she gives Harry, who needs a tungsten-type figure in his life as he can be a bit of a softy. It's become a term of endearment," an insider explained to the publication.
Last month, Woman's Day revealed how the 36-year-old helped mend Prince Charles and Prince Harry's relationship.
It's said Prince Harry hasn't forgiven his father for the way he treated Princess Diana, and Charles has long despaired over his youngest son's wayward behaviour as a teen, bringing the monarchy into disrepute.
"Meghan's first priority was winning over her future father-in-law," a source said.
"At first Harry couldn't believe she was going to so much effort, but the more time they spent with Charles, the more Harry realised he must bury the hatchet."Harry was very touched by how welcoming Charles was to Meghan who, though confident, must have found adapting to royal life hugely intimidating. Charles played a huge part in making her feel at home."
By the time the wedding rolled around, Meghan and Charles were firm friends.
"Are you all right? You look lovely," Charles is believed to have whispered to her, earning him new fans around the world.
Further cementing Harry, 33, and Charles' newfound closeness is how he's taken care of Meghan's mother Doria.