Kate Middleton has a big thing in common with this royal

Kate Middleton is having a busy week. She is on a rare solo trip to Denmark for two days. Yesterday, she visited the Copenhagen Infant Mental Health Project at the University of Copenhagen - wearing a gorgeous sustainable pearl necklace - and this morning she attended an event at the Stenurten Forest Kindergarten.

Next up, a visit with the Danish royals. The Duchess of Cambridge met with the country's Queen Margrethe and Crown Princess Mary at Christian IX’s Palace in Copenhagen, where they had a private lunch.

Catherine and Mary then headed over to the Danner Crisis Centre, a shelter that helps women who have been exposed to domestic violence. It's supported by the Mary Foundation, which was founded by the Crown Princess in 2007.

On their way there, the two royals had a laugh and were photographed deep in conversation. It's thought the two have grown quite close since they first met in 2011, and they attended Royal Ascot together in 2016 with their husbands, Prince William and Prince Frederik.

One of the reasons the women may be so close is their similar backgrounds, since neither of them came from a royal or noble family.

Kate met William at the University of St. Andrews in 2001 while Mary, who is Australian, met Frederik at the 2000 Olympics. She had a career in advertising before moving to Denmark to become a royal.

So you can imagine both women have a lot of similar experiences to share, having joined royal families from different backgrounds.