Pippa Middleton and husband James Matthews have named their son Arthur.
Revealed in the UK's Mail On Sunday, the Duchess of Cambrige's sister, 35, welcomed her baby boy weighing 8lb and 9oz at the private Lindo Wing, at St Mary's Hospital, Paddington, last month but at the time his name was kept under wraps.
The couple have also given their baby boy the middle names Michael and William.
The name Michael is a touching tribute to Pippa's father and her husband's younger brother who died while climbing Mount Everest in 1999.
Michael Matthews went missing on the mountain's infamous Death Zone while he was trying to become the youngest Briton to climb the world's highest peak.
Following his tragic death brother James Matthews accompanied by wife Pippa have become committed to fundraising for poverty-stricken areas in Africa and Asia through the Michael Matthews Foundation
The birth of the couple's baby came just hours after Prince Harry and Meghan Markle announced they were expecting a child.
Last month Ms Middleton and her husband were seen arriving at the same unit of the maternity wing where sister Kate Middleton had given birth to her three children George, Charlotte and Louis.
On baby Arthur's birth certificate mother Pippa Middleton's profession is also listed as author.
Her book Celebrate, which gave readers advice on party-planning, was panned for offering "painfully obvious" advice when it was published in 2012.