Queen Elizabeth II and Prince Philip have a love story for the ages. ET is looking back at the couple's romance following Philip's death on Friday, April 9, at age 99.

Elizabeth and Philip, who were married for 73 years, welcomed four children together and stayed by each other's side for many historical and personal events of the last century. 

Their romance started when Elizabeth was just 13 years old and continued until Philip's death. 

Look back at how it all began and the journey of the most successful royal couple:

First Meetings

Elizabeth first met Philip in 1939 when she was just 13 years old. At the time, he was the Prince of Greece and five years older than her, preparing to start a career in the Royal Navy. Elizabeth's cousin, Margaret Rhodes, wrote in her autobiography, "Elizabeth was truly in love from the very beginning." 

Engagement 

Years later in 1946, Philip asked King George VI for Elizabeth's hand in marriage. The king made Philip wait to formally announce the news until Elizabeth turned 21 the next April, forcing the couple to keep their engagement a secret for a year. 

On Nov. 20, 1947, Philip and Elizabeth were married in a stunning royal wedding ceremony at Westminster Abbey. At the couple's wedding breakfast, King George VI declared, "Our daughter is marrying the man she loves." 

Honeymoon

Elizabeth was clearly head over heels for Philip, telling her parents in a letter from her honeymoon that she and the Duke of Edinburgh "behave as though we had belonged to each other for years!" adding, "Philip is an angel." Philip also gave up smoking for his wife and would go on to give up his post in the Navy when she took the throne. 

A Baby Boy

Almost exactly one year later, Elizabeth and Philip welcomed their first child -- Prince Charles. The young family later took up residence in Malta for several years, where Philip was stationed in the Royal Navy. They welcomed their second child, Princess Anne, in 1950. 

Coronation

On June 2, 1953, Elizabeth officially became Queen Elizabeth II as she ascended to the British throne. Philip proudly stood by her side in full naval uniform. While Prince Charles was on hand to witness his mother's coronation, a then-2-year-old Princess Anne was considered too young to attend the ceremony. 

Commonwealth Tour

Following Elizabeth's coronation, the couple ventured off on their own for a six-month tour of the Commonwealth. They would go on many other royal tours together throughout their marriage. 

Life With Their Kids

Elizabeth and Philip welcomed sons Prince Andrew and Prince Edward in 1960 and 1964, respectively. Following extended absences in their younger years, the teenage children enjoyed time with their parents as they grew. 

50th Anniversary

For the couple's 50th wedding anniversary, Prince Philip gave a rare speech about their marriage, saying, "I think the main lesson that we have learnt is that tolerance is the one essential ingredient of any happy marriage. It may not be quite so important when things are going well, but it is absolutely vital when the going gets difficult. You can take it from me that the queen has the quality of tolerance in abundance."

Elizabeth also shared her affection for her husband, saying, "He is someone who doesn't take easily to compliments but he has, quite simply, been my strength and stay all these years, and I, and his whole family, and this and many other countries, owe him a debt greater than he would ever claim, or we shall ever know." 

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Royals in Quarantine 

Prince Philip retired from royal life in 2017, making the occasional public appearance in the time since. But following the coronavirus pandemic, Philip and Elizabeth spent much of their quarantine together at Windsor Castle. 

"[Philip] is in self-isolation with the queen, which I'm told they're surrounded by a very small team of staff," royal expert Katie Nicholl previously told ET. "Just a handful of staff between the two of them, which must be quite enjoyable for them not to have the formality of so many courtiers, which is what the queen is used to when she's at Buckingham Palace."

Philip and Elizabeth's grandson, Prince Harry, previously confirmed that the two royals regularly did Zoom calls with members of the royal family. 

"Both my grandparents [use Zoom]," Harry said on The Late Late Show With James Corden. "We've Zoomed them a few times. They've seen Archie running around. My grandfather, instead of pressing 'Leave Meeting,' he just goes [mimes abruptly closing the computer]," Harry added, laughing. 

Enduring the Test of Time

After more than seven decades of marriage, four children, their fair share of personal drama and scandal, and plenty of milestones, Elizabeth and Philip were clearly built to last. Lord Charteris, the private secretary of the queen, is quoted as saying, "Prince Philip is the only man in the world who treats the queen simply as another human being. He's the only man who can. Strange as it may seem, I believe she values that."