LOS ANGELES (Reuters) - The most famous babies on the planet, the latest spawn of Angelina Jolie and Brad Pitt, made their world premiere on the Internet on Sunday, having outfoxed the paparazzi since they were born three weeks ago.

People magazine posted the cover of its upcoming issue, featuring twins Vivienne Marcheline and Knox Leon and their proud parents, on its Web site, a teaser for a 19-page spread that will hit newsstands on Monday.

All were dressed in white, and the babies had no distinguishing characteristics. A smaller photo in the corner showed the couple's 2-year-old daughter, Shiloh, holding her new sister.

In a blurb that accompanied the cover photo, Jolie was quoted as saying that the couple's family life at a sprawling French chateau was "chaos, but we are managing it and having a wonderful time."

In addition to the twins and Shiloh, the couple has three adopted children. Jolie, 33, and Pitt, 44, are one of Hollywood's most glamorous couples, dubbed "Brangelina" by the celebrity press. She gave birth to the twins in the French city of Nice. Hordes of paparazzi waited out the process, but were unable to penetrate the hospital's heavy security.

The shoot was conducted by photo agency Getty Images, with People acquiring North American rights to the photos, and British gossip magazine Hello! all other territories. The Pitts have said they will donate the proceeds to charity.

The sum involved has developed into an international guessing game. Rumored price tags for Hollywood baby photos are often wildly inaccurate, and Radar magazine recently reported that celebrity publications are not above stoking the hype in order to boost newsstand sales and Web site traffic.

In the case of the Jolie-Pitt twins, an unsourced report claimed the worldwide rights sold for $14 million, more than three times the rumored $4.1 million deal for Shiloh's baby photos in 2006. People has said that the rumored numbers for both deals, as well as those for other famous babies that have adorned its pages, are excessive. But it has declined to elaborate.

(Reporting by Dean Goodman)