Pippa Middleton, the sister of Kate Middleton (aka the Duchess Cambridge), who turned 28 on Sept. 6, couldn't celebrate her birthday in style.

Amidst the rainy weather, Pippa enjoyed her birthday morning with her cup of coffee along the way going to work. Pippa was seen carrying her umbrella and her briefcase.

Pippa's sister is the beautiful and brilliant Kate Middleton, the wife of Prince William, the heir to the British throne. Kate was in London but there was no plan for celebrating her little sister's birthday.

There was no game or party for Pippa, who turned 28 on Tuesday. However, Pippa was spotted having lunch and enjoying shopping with a new mystery man. It is posssible that Pippa bought some birthday gift.

Pippa has gained worldwide recognition for being the Duchess of Cambridge's sister.

Hopefully, Kate Middleton had some plans to celebrate her little sister's birthday. Happy Birthday to you, Pippa!

Pippa Middleton leaves The Goring Hotel in London
Pippa Middleton leaves The Goring Hotel in central London, on April 30, 2011. REUTERS
Pippa Middleton watches a match during the French Open tennis tournament at the Roland Garros stadium in Paris
Pippa Middleton, sister of Catherine, Duchess of Cambridge, watches the match between Maria Sharapova of Russia and Agnieszka Radwanska of Poland during the French Open tennis tournament at the Roland Garros stadium in Paris, on May 30, 2011. REUTERS
Pippa Middleton at the Wimbeldon Tennis Championships
The sister of Catherine, Duchess of Cambridge, Pippa Middleton, sits at Centre Court for the quarter-final match between Jo-Wilfried Tsonga of France and Roger Federer of Switzerland at the Wimbledon Tennis Championships in London, on June 29, 2011 REUTERS
Pippa Middleton watches a match during the French Open tennis tournament at the Roland Garros stadium in Paris
Pippa Middleton (L), sister of Catherine, Britain's Duchess of Cambridge, watches the match between Maria Sharapova of Russia and Agnieszka Radwanska of Poland during the French Open tennis tournament at the Roland Garros stadium in Paris May 30, 2011. REUTERS
Britains Prince Harry and Pippa Middleton stand on the balcony of Buckingham Palace in London
Britain's Prince Harry (R) and Pippa Middleton stand on the balcony of Buckingham Palace, following following the wedding of Prince William and Kate Middleton at Westminster Abbey in London April 29, 2011. REUTERS
Kate middleton London London