Transcript for Prince William, Duchess Kate welcome baby boy to the royal family

And from London tonight, a more welcome headline, the newest member of the royal family. Take a look. Kate with her new son, and right beside her, that photograph of Diana, a lot of comparisons today, given the color of the clothes and holding the baby. That was Harry, by the way. And look at this from today. Big sister Charlotte coming to meet her little brother. Charlotte turning around, though, to give the crowd an extra wave. Stealing their hearts. ABC's James Longman from London. Reporter: Wrapped up tight, take a look at Britain's newest prince. A third child welcomed today by Catherine and her husband prince William. The duchess was admitted to the private wing of St. Mary's hospital in London at 6:00 A.M. This morning, going into lay before right on her due date. And news of the birth came soon after, a little boy. So the official sign outside Buckingham palace read, "Born five hours later, weighing eight pounds and seven ounces." The anticipation huge here, waiting for news of that little boy. Prince William leaving to collect George and Charlotte. Crowds treated to a royal wave from the young princess. And then after, climbing those stairs, another look back and one more wave. This new prince will be fifth in line to the British throne, ahead of prince Harry, but he won't leapfrog his older sister Charlotte now that the rules of succession have changed. A younger brother no longer jumps in front of an older sister. As William put his new son in the car for the short drive home, the dad of three revealing what's on his mind. Very happy, thrice worry. Reporter: No name just yet for the youngest royal. James, Arthur and Phillip all possibilities. And James Longman joining us now from outside kensington palace. The world met the new baby today, but not by name. At least not yet. How long do we usually wait? Reporter: Well, it did take a couple of days when Charlotte was named, and they might, of course, like to run it past the queen. We are all waiting to hear very soon, we hope.

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