Profile: Catherine, Duchess of Cambridge
The Duchess of Cambridge has moved from a comparatively ordinary existence to a prominent role in the Royal Family.
She became Prince William's girlfriend in 2001, the couple having met while studying at St Andrews University, Fife, where they shared student digs.
Their wedding at Westminster Abbey some 10 years later, in April 2011, was watched on television by millions of people around the world.
The announcement in December 2012 that the couple were expecting their first child - and the subsequent arrival of Prince George - thrust the duchess into the media spotlight like never before.
And that spotlight is shining brightly on the young royals again with the news that the 14-month-old prince is to be joined by a brother or sister.Popular and talented
Catherine Middleton was born on 9 January 1982.
She grew up in Bucklebury, Berkshire, where her parents, Michael and Carole Middleton, run a mail-order business selling toys and games for children's parties from a converted barn close to their home.
The eldest of three children, she was educated at the exclusive Marlborough College in Wiltshire, where she was described as level-headed, popular and talented, and captained the school hockey team.
Her sister Pippa, 31, has raised her profile since she was maid of honour at the royal wedding. She has written a party-planning book and also writes for magazines.
Her brother, James, 27, has founded a baking company.
After they met at St Andrews, where Catherine studied art history, the young couple's relationship apparently flourished during weekends together on the Queen's Balmoral estate.
For a while, at least, they were guaranteed some privacy, following an agreement worked out between the palace and press while Prince William was a student.
But the media silence did not last, and Catherine was first brought to the public's attention after several tabloids pictured her beside Prince William and Prince Charles at the Swiss ski resort of Klosters in 2005.
The photographs appeared despite efforts by aides to keep the holiday private.
Newspaper interest grew when Catherine graduated, moved to London and started work as an accessory buyer for High Street clothes shop Jigsaw.
In October 2005, after the publication of a photo which showed her looking out of a window on a London bus, her lawyers wrote to newspaper and magazine editors asking them to respect her privacy.
They claimed photographers had followed Catherine almost every day and night since she left university.
Speculation over an engagement was sparked in February 2006, when it was suggested she would receive her own royal security.
In December 2006, Catherine was again in the headlines after she and her mother attended a ceremony at Sandhurst Royal Military Academy, to watch Prince William being commissioned as an army officer.
The occasion was notable as the first time she had been seen at a high-profile public event attended by the Queen and other senior royals.Media pressure
Rumours of an engagement reached a peak around the time of Catherine's 25th birthday in January 2007, when the media scrum took up residence outside her Chelsea home.
The paparazzi free-for-all drew inevitable comparisons with the prince's late mother, killed in a car crash in Paris while being pursued by photographers.
Prince William and Prince Charles appealed for her to be left alone, and some newspapers agreed to stop using paparazzi shots of her.
Media pressure appeared to take its toll and was blamed when the couple split in April 2007, although no official statement was issued by either.
Reports of a reconciliation were denied in June 2007, with the couple insisting they were "just good friends" after being spotted together at the Concert for Diana at Wembley.
They were then seen in public on a number of occasions.
Catherine was present when the prince received his RAF wings from his father at RAF Cranwell in April 2008 and in Windsor when he became a Knight of the Garter in June.
The couple announced their engagement in November 2010, and at the time Catherine said joining the Royal Family was a "daunting prospect".
"Hopefully I'll take it in my stride," she added.Charity support
The duchess supports a number of charitable organisations through her own charity, the Royal Foundation of The Duke and Duchess of Cambridge and Prince Harry.
She is also patron of Action on Addiction, East Anglia's Children's Hospices, the Art Room, National Portrait Gallery, Place2Be, SportsAid and the Natural History Museum.
In December 2012, St James's Palace announced that the Duchess of Cambridge was expecting a baby, and that Catherine had been admitted to hospital with acute morning sickness.
She stayed in hospital for several days before being discharged, but her stay was marred by the suicide of nurse Jacintha Saldanha after two Australian DJs made a hoax call to the hospital.
Baby Prince George was delivered on 22 July 2013 at 16:24 BST, weighing 8lbs 6oz, in the private Lindo Wing of St Mary's Hospital in Paddington, west London - where Princess Diana gave birth to her sons.
The couple spent the first few years of married life on Anglesey, north Wales, where the Duke of Cambridge worked as a search and rescue pilot with RAF Valley.
But, following the announcement that the duke was leaving the military, the couple left the island to set up home in a refurbished apartment in Kensington Palace, London.
Prince William is due to start a new role as an air ambulance pilot, flying with the East Anglian Air Ambulance, next spring.
Now, months after Prince George's first birthday, they say are "very pleased" to announce that the duchess is expecting her second child.
She and Prince William have undertaken three official overseas tours together - to North America and Canada in 2011, to South East Asia in 2012 to mark the Queen's Diamond Jubilee and to Australia and New Zealand in April 2014.
The duchess is due to visit Malta later this month in her first official overseas trip without Prince William - it is unclear if that will go ahead now that she is pregnant again.