Spain's monarchs wrote a letter to the queen after Prince Philip's death that nods to a little-known connection between the families

• Spain's king and queen wrote a personal letter to Queen Elizabeth II after Prince Philip died.
• They wrote about "dear Uncle Philip," nodding to the blood relation between their families.
• Other European royal families shared memories of Prince Philip after his death.

Spain's King Felipe VI and Queen Letizia are among members of royal families around the world who shared messages on social media or sent condolences to the queen after Prince Philip's death on Friday.

The Spanish royal couple's letter to the queen also included some personal touches that referenced the connection between their families.

The BBC and Hola magazine reported that in their letter, the Spanish royals addressed the queen as "Aunt Lilibet," which nods to one of the queen's family nicknames.

The name Lilibet came about when the queen was still Princess Elizabeth, and it might have been coined by her grandfather, according to royal biographer William Shawcross. The nickname might have also been reflective of how she pronounced her first name, Elizabeth, as a child.

In their letter, according to Hola, King Felipe VI and Queen Letizia continued: "We were deeply saddened to hear of the passing of our dear Uncle Philip."

The Spanish royals' letter didn't address the queen as "Aunt" and describe the duke of Edinburgh as "our dear Uncle Philip" by coincidence. King Felipe VI has distant ties to the British royal family. His maternal great-grandfather, King Constantine I of Greece, was Prince Philip's uncle.

Prince Philip was born to Prince Andrew of Greece and Denmark, the brother of King Constantine I of Greece.

So while Prince Philip and Spain's King Felipe VI were related distantly (they weren't simply "uncle" and "nephew") the letter to the queen underscored their families' blood connection.

"We will never forget the occasions we were able to share with him and the legacy of service and dedication to the Crown and the United Kingdom that he always carried out at your side. Our thoughts and prayers are with Your Majesty and the whole family," the letter said, according to Hola.

The couple signed the letter with "love and affection."

Other royal families remembered Prince Philip's life and career in statements after his death.

Tributes included messages from the Dutch royals King Willem-Alexander, Queen Máxima, and Princess Beatrix, who said Prince Philip's "lively personality never ceased to leave an unforgettable impression."

King Philippe and Queen Mathilde of Belgium also said they would "always cherish the memories of our warm encounter" with the duke, according to the BBC.

Representatives for Buckingham Palace did not immediately respond to Insider's request for comment.