An unnamed charity could be £5m better off today after the birth of Brad Pitt and Angelina Jolie's twins.

The bidding war has already begun for the first photos of Knox Leon and Vivienne Marcheline who were born on Saturday night at a French hospital.

French papers have reported that an American magazine has already offered $10m (£5m) for the exclusive images of the new babies  -  with all the money going to a worthy cause.

Blooming: Pregnant Angelina Jolie at a Cannes film festival photo call in May

After the birth of their daughter Shiloh two years ago, the couple auctioned off the photo shoot to People magazine in the US and Hello! in Britain for up to £5m with an undisclosed charity benefiting.

It is believed Pitt and Jolie are in the process of negotiating a similar deal for the photos of the latest additions to their family.

The twins were born one minute apart with Pitt by Jolie's side as the doctor performed a Caesarean section to deliver Knox and Vivienne  -  both weighing 5lb.

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Nice mayor Christian Estrosi (centre) holds copies of Brangelina's new son Knox Leon Jolie-Pitt's birth certificate as Angelina's doctor Michel Sussman (left) and hospital director Bernard Lecat look on

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Knox Leon Pitt-Jolie's birth certificate (click to enlarge)

Jolie's obstetrician, Dr Michel Sussmann, said: 'Mother, the babies, and the father are doing marvellously well.' He said the Caesarean was moved forward from its originally planned date 'for medical reasons' so the babies could be born 'in the best conditions.'

He said 33-year-old Miss Jolie was under epidural and able to speak to a 'perfectly calm' Pitt during the birth.

He added that Jolie, 33, is expected to stay and rest at the exclusive Lenval hospital in Nice for the next few days and is already enjoying specially couriered-in food for her stay.

'Angelina is in very good spirits. Brad Pitt was at her side. The mother and father are very, very happy.'

The actress is then expected to depart as she arrived  -  in a helicopter taking off from the roof of the building, most likely in the dead of night to avoid being photographed.

Vivienne's middle name was chosen in honour of Jolie's mother, actress Marcheline Bertrand, who died in January last year after a seven-year battle with cancer.

Miss Bertrand raised Miss Jolie and her brother, James Haven, after divorcing their father, actor Jon Voight, when Miss Jolie was three.

The arrival of the twins brings the couple's family to six. They are already parents to three adopted children: Cambodian boy Maddox, six, Vietnamese boy Pax Thien, four, and Ethiopian girl Zahara, three.

Their natural daughter Shiloh, two, was born in Namibia in 2006.

Proud parents: Angelina has given birth to a healthy boy and girl in the French Riviera

Miss Jolie arrived at the Lenval hospital in late June, provoking a media circus with photographers desperate for a picture of the mother-to-be.

Yesterday, news of the births spread like wildfire through the streets and markets of Nice.

The mayor, Christian Estrosi, seized the opportunity to promote his city by arriving at the hospital to sign the birth certificates wearing a smart suit and full make-up for the TV cameras.

View of the Lenval Hospital in Nice where US actress Angelina Jolie has given birth to twins

'I congratulate the happy parents, who have chosen our city for this happy event,' he said. 'The newborns are, history will not forget it, real Nicois, citizens of Nice.'

Miss Jolie and Pitt, 44  -  who met on the set of 2005 film Mr & Mrs Smith, when Pitt was still married to Friends star Jennifer Aniston  -  own a 17th century villa in the village of Correns in Provence.