Amongst her in-laws, the new mum is closest to Sophie, the Countess of Wessex and Camilla, the Duchess of Cornwall – both of whom have spent the last few years helping her ease into her role as a royal consort. Sophie and Kate are often seen giggling together at Windsor get togethers.
Another possibility is to pay tribute to Camilla by asking one of her children – Tom Parker Bowles or Laura Lopes.
William is also friendly with his cousin Peter Phillips, who recently praised his and Kate's potential as parents. Peter's sister Zara is an option too.
Within the royal family the Cambridges may also ask Sophie and Peter Phillips
William's best friend
The future King's best friend from Ludgrove prep school and Eton is Thomas van Straubenzee, who married the Duke of Northumberland’s daughter – Lady Melissa Percy of Alnwick Castle in the society wedding of the year just before Kate gave birth. The two buddies travelled to New Zealand together during their gap years.
William and Harry are patrons of a foundation in the name of Thomas' brother Henry, who was killed in a car crash 11 years ago.
Thomas van Straubenzee is William's closest childhood friend
Alicia Fox-Pitt is the Duchess' best friend from Marlborough.
It was the athletic red head who roped Kate into the Sisterhood rowing team, which planned to cross the Channel during her brief split from the Prince in 2007. The Berkshire girl dropped out when their romance reignited. Alicia recently married entrepreneur Sebastian Stoddart.
Others in the Marlborough set include Hannah Gillingham, Catriona Foyle, and Alice St John Webster. These ladies have been BFFs since the age of 14 and will all have children about the same age as George.
Alicia Fox-Pitt is Kate's best friend from Marlborough
Charles' family friends
Hugh van Cutsem's ties with the royal family go back over 40 years when his father Hugh senior was at Cambridge with Prince Charles.
He is married to Lady Rose Astor and their daughter Grace was a bridesmaid when the Duke and Duchess tied the knot. The little girl is also William's goddaughter – making it likely he'll return the favour.
Hugh has three brothers – Edward, Nicholas and William – who have all grown up with the Princes. Edward is another option; his wife Tamara is the daughter of the Duchess of Westminster, Tally, who was a friend of Princess Diana's and was the Duke's godmother.
Tiggy Pettifer née Legge-Bourke
She helped bring up the Princes after the divorce of their parents. Sensible, warm and jolly good fun, Tiggy declared William and Kate's engagement "fan-flaming-tastic". The new dad is godfather to her son Tom, who was a page boy at the royal wedding.
Greek royal family
Constantine II, the former King of Greece, is godfather to the Queen's grandson.
William is in turn godfather to the King's 14-year-old grandson and namesake. The younger Constantine is the son of Crown Prince Pavlos and his wife Marie-Chantal. It's possible that Pavlos or even the teenager himself may be given this honour in relation to Britain's newest heir.
The Windsors have longstanding links with the Greek royal family because Prince Philip is the grandson of George I of Greece.