Prince Harry joked recently that he hoped his brother knew "how expensive my babysitting charges are" and also vowed to teach his nephew to have fun.
Whether his offer was a promise or a threat, given his most recent antics in Las Vegas, remains to be seen.
But the 28-year-old helicopter pilot was clearly already besotted with his new nephew Prince George.
The prince went to see the new family addition at Kensington Palace shortly after his brother and sister-in-law returned from hospital on Tuesday night.
As he spoke he gestured with his hands and described George as being "about this long and that wide".
"When I saw him he was crying, which is just like all babies," he said.
"It's fantastic to have another addition to the family. I only hope my brother knows how expensive my babysitting charges are!"
— Daily Mail