The lowdown on royal highnesses: a packed agenda for Prince William, Kate in NYC, Washington

NEW YORK — Among the roughly 5 million visitors expected in New York this holiday season, at least two are certain to get the royal treatment: Britain's Prince William and his wife, Kate. They're due to arrive Sunday for the first trip either has made to the United States' biggest city, and William also is set to visit the nation's capital for the first time. A few things to know:

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THE GAME PLAN

Properly known as the Duke and Duchess of Cambridge, the royals are making their first official visit to the United States since a 2011 jaunt to California. (William made a personal trip to a friend's Memphis, Tennessee, wedding this May with his brother, Prince Harry.)

The duke and duchess have been looking forward to a three-day trip involving issues "close to both of their hearts," a spokeswoman said.

Kate is expecting their second child in April, but the royals' schedule is packed with plans ranging from paying respects at the National Sept. 11 Memorial and Museum to taking in a Cleveland Cavaliers-Brooklyn Nets game.

Other events promote British involvement in New York's technology and creative sectors and spotlight the couple's charitable interests in wildlife conservation and child development. Among other commitments, William will head to a World Bank conference in Washington to discuss fighting illegal trade in wildlife parts, while Kate will tour a New York child development center with the city's first lady, Chirlane McCray.

As an itinerary, "it's trying to cover a lot of points in a short period of time," but it signals the couple's interest in forging ties with Americans who share their philanthropic ideas, says Joe Little, the managing editor of Majesty magazine.

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NYC, ROYALTY AND 'ROYALS'

Spain's Queen Letizia toured a public school just in September. Among British royals, Queen Elizabeth II visited in 2010, and Prince Harry hit both New York and Washington last year. The queen's daughter, Princess Anne, opened an exhibition of the Magna Carta in Washington last month.

But William and Kate's watched-round-the-world wedding and parenthood have made them particular magnets for public attention, as a 21st-century royal family in which an heir to the throne drives his newborn home from the hospital himself.

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TRAVELING, WITH A TITLE

The duke and duchess will take commercial flights and stay in a New York hotel, which their spokespeople wouldn't name.

Their retinue includes two private secretaries, two media aides, an adviser, a personal assistant, and a privately paid hairdresser for Kate. The British government's Foreign and Commonwealth Office, the Royal Foundation — the couple's and Harry's charity — and St. Andrews are splitting other trip costs.

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The couple's 17-month-old son, Prince George, isn't making the trip.

Acute morning sickness sidelined Kate for a couple of months earlier this year, but she returned to her royal duties with gusto in late October.

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STYLE GUIDE

While the royals promote causes, many eyes will doubtless be on Kate's clothes. A style icon whose outfits can sell out in stores within hours after she's seen in them, she's won fashion-lovers' affection partly because she doesn't always choose complex or custom-made attire: "There's a connection — you can get it," or at least a copy of it, says Michael Casey, a professor at New York's Fashion Institute of Technology.