Pregnant Kate Middleton and Prince William Make an Elegant Pair at the Queen’s Anniversary Party

[MUSIC] [MUSIC] [MUSIC] [BLANK_AUDIO]

On Monday, Nov. 20, Queen Elizabeth and Prince Philip celebrated a milestone in their odds-defying marriage: their 70th wedding anniversary.

How do royals celebrate seven-decades of partnership? It’s three-fold, really. There are the official portraits, the honorary knighthood, and the epic party at Windsor Palace—us, too.

According to People, the Queen, 91, and Philip, 96, celebrated alongside their children Prince Charles, Princess Anne, Prince Andrew, and Prince Edward, as well as grandson Prince William and Duchess Kate Middleton.

William and Kate were spotted at the event in elegant black ensembles. The Prince opted for a classic tuxedo, while Middleton wore a dress that looked similar the black lace Diane Von Furstenberg gown both she and prospective sister-in-law Meghan Markle own (in different lengths). The mother of two (soon to be three!) paired the garment with a three-strand pearl choker with a diamond centerpiece and silver drop earrings. If the statement necklace looks familiar, it's because she borrowed it from Queen Elizabeth and it's also been worn by Princess Diana.

RELATED: See Queen Elizabeth and Prince Philip's (70th!) Anniversary Portrait

We’ve got to commend Middleton on her activity over the past couple months. Despite extreme morning sickness and the glare of the unrelenting spotlight, the Duchess of Cambridge still finds time and energy for those she loves.

Congratulations to Queen Elizabeth and Prince Philip on their inspiring 70-year-long love story—we're sure William and Kate have learned a thing or two from their enduring relationship.