Pippa Middleton is pregnant with third child

Kate Middleton's sister debuted her baby bump at the Jubilee concert

Pippa Middleton surprised onlookers with what is thought to be a baby bump at the Party at the Palace at Buckingham Palace Saturday.

A source confirmed to Page Six that Kate Middleton’s younger sister was pregnant with her third child with husband James. 

Middleton, 38, married James Matthews, 46, a hedge fund manager and former racing driver in 2017 and the couple are already parents to three-year-old Arthur, and one-year-old Grace. 

Pippa fuelled pregnancy speculation at the Buckingham Palace concert on Saturday, wearing an ruched emerald ME+EM dress accessorised with her diamond wedding ring and coiffed ringlets. 

She stood alongside her parents Carole and Michael and younger brother James and his wife Alizée Thévenet at the concert, while her older sister the Duchess of Cambridge sat in the royal box with Prince William and their oldest children Prince George and Princess Charlotte. 

Pippa, who attended the concert without her husband, is very close with her sister and gave birth to her two children at the Lindo Wing of St. Mary’s Hospital, like Kate. 

The couple split their time between their six-bedroom Chelsea mansion, which is valued at around £17million. The family also own Bucklebury Farm, a 70-acre deer and safari park in West Berkshire, which they purchased in 2018.

The Party at the Palace seems to be the only event the Middleton family took part in across the Jubilee weekend, which concluded on Sunday with an impressive pageant on the Mall, that included a performance by Ed Sheeran and guests included Kate Moss and Cliff Richard.

The Jubilee kicked off with the Trooping the Colour and the lighting of the platinum beacons on Thursday, followed by a Service of Thanksgiving on Friday, attended by Prince Harry and Meghan Markle. Saturday highlights included the BBC concert and the Epsom Derby.