Pippa Middleton Celebrates Birthday Today in NYC, Apartment Hunting?

Thursday has arrived as Pippa Middleton's 29th birthday and Catherine, Duchess of Cambridge's little sister, is celebrating in New York City.

The royal sibling was spotted at the U.S. Open quarterfinal on the eve of her birthday Wednesday donning a lacy yellow dress paired with nude wedges.

While watching Andy Murray earn a victory during the tennis match, Middleton was seated beside handsome tennis player Spencer Vegosen. The pair laughed and joked during the game, spurring even more rumors about Middleton's love life.

Middleton's trip to New York City arrives just weeks ahead of the launch of her new book, "Celebrate: A Year of Festivities for Families and Friends," and the style icon has scheduled meetings and promotional events for it.

The media has been in a frenzy around Middleton's visit to the U.S., with the royal sibling making international headlines after spending time in the Hamptons with wealthy hotel owner Andre Balazs. Afterward, she was spotted at a number of NYC hotspots, including seafood restaurant Catch as well as the Downtown Dream hotel's Electric Room with former New York Ranger Sean Avery.

Moreover, rumors swirled that Middleton is considering moving from her native London to New York City. Kate's sister was spotted at a residential building in Manhattan with what appeared to be a realtor on Wednesday, according to the Daily Mail.

One of the biggest fashion events of the year, New York Fashion Week, has officially kicked off in the metropolis this week, and many hope that Middleton attends the week's events.

Unlike her sister, who is known to recycle dresses, Pippa tends to wear bolder fashions and has never been photographed in the same outfit twice.

Thursday also marks an important night of New York Fashion Week- Fashion's Night Out, where many luxury brands will hold public events offering limited-edition products and celebrity appearances.

In honor of the event, Manhattan's Empire State Building will be lit in red lights on Thursday night.