Lord and Lady Nicholas Windsor welcomed their third child on May 27 and named their son Louis Arthur Nicholas Felix. Louis’ older brothers are Albert Louis Philip Edward, aged nearly seven, and Leopold Ernest Augustus Guelph, aged nearly five. Louis is 37th in line to the throne, and is to be known as Mr Louis Windsor.

Lord Nicholas is the youngest son of the Duke and Duchess of Kent, and a great-grandson of King George V. Prince Edward, the Duke of Kent, is a cousin of Queen Elizabeth, so Lord Nicholas is a first cousin once removed of the queen. In 2001, Lord Nicholas was received into the Roman Catholic Church, following the lead of his mother Katharine, who converted in 1994. This makes him the first male member of the blood Royal to convert to Catholicism since King Charles II. Because of his conversion, he forfeited the right of succession to the British throne, but is still in the line of succession to the Dukedom of Kent.

Lady Nicholas Windsor was born Paola Doimi de Lupis de Frankopan; her father is a member of the Croatian and Italian nobility, while her mother is a distinguished Professor Emeritus at Stockholm University. Under her maiden name Paola Frankopan, she writes for The Tatler, where she is a contributing editor. She and Lord Nicholas were married on September 4 2006 in Vatican City, making Lord Nicholas the first member of the Royal Family to marry at the Vatican, and the first to marry in a Catholic ceremony since the Reformation. By having Louis shortly before her 45th birthday, Lady Nicholas became the oldest royal to give birth.

Louis is most likely in honour of Lady Nicholas’ father, Louis, Prince de Frankopan, Count Doimi de Lupis, a barrister and businessman. The children’s maternal grandfather was earlier honoured by having Louis as Albert’s middle name. Louis also has a Catholic saint’s name, like his brothers Albert and Leopold.

Arthur has previously been used in the royal family; most recently by Prince Arthur of Connaught, the son of Prince Arthur, son of Queen Victoria. Perhaps coincidentally, Arthington is a name traditionally used in the family of Lord Nicholas’ mother Katharine, whose maiden name was Worseley.

Nicholas is after the baby’s father. It is one of the middle names of Prince Edward, Duke of Kent, the father of Lord Nicholas, and Prince Nicholas of Greece and Denmark was Prince Edward’s grandfather, the father of Princess Marina, Duchess of Kent. Lady Nicholas’ brother is also named Nicholas, so it’s a name from both sides of the family.

Felix may be in honour of Lord Nicholas’ great-uncle, Sir Felix Brunner, 3rd Baronet, the uncle of his mother Katharine (and her godfather) The meaning of “lucky” seems apt, because the Windsors were not expecting to have any more children, and felt very fortunate to be blessed with a child; indeed Louis has been hailed as a “miracle baby”.

(Photo of Lord and Lady Nicholas Windsor with their two eldest sons from Hello!)