Pippa Middleton and James Matthews welcome their third child

Pippa Middleton has welcomed a baby girl, her third child with her husband James Matthews. Photo / Getty Images

Pippa Middleton has welcomed her third child.

People Magazine has reported the younger sister of Kate Middleton and her husband, James Matthews have welcomed their third child, a baby girl.

Their new baby girl joins their son, Arthur, 3, and 16-month-old daughter, Grace.

The couple is yet to reveal their new baby's name or date of birth but the publication reported the 38-year-old gave birth "a couple of weeks ago in the Lindo Wing of St. Mary's Hospital in London."

It is the same hospital the Duke and Duchess of Cambridge welcomed their three children.

The couple – who married in 2017, quietly announced their happy news on June 4 at the Queen's Platinum Jubilee when the duchess's younger sister was seen cradling her bump in a bright green dress at the Platinum Party in the Park concert outside Buckingham Palace.

Appearing at the Platinum Party at the Palace, Pippa Middleton had a notable baby bump. Photo / Getty Images

The happy news comes after a source revealed People Magazine the duchess's younger sister is planning to move to a village near Bucklebury in Berkshire to be closer to family.

The Middleton sisters grew up in Berkshire and their parents still live there while Prince William, Kate and their three children, George, 8, Charlotte, 7, and Louis, 4, are relocating to Windsor in the coming months which will be a short 50-minute drive from Berkshire.

While Pippa is relatively private about her personal life, she opened up about keeping fit with her family in an interview with sportswear label Hoka One, last year.

The couple who wed in 2017 now share three children together. Photo / Getty Images

"Being active with my 2.5-year-old son in the park or playground, transporting him on the back of my bike and buggy running when he was a baby have been ways in which I have been able to include outdoor exercise whilst being a hands-on mummy," she said.

Adding, "Being such an active family has rubbed off on my son. He loves nothing more than running wild in the woods, parks and fields with our two dogs, even if it's howling a gale and pouring with rain."