Prince George and Princess Charlotte could pay a visit to the Lindo Wing to meet their new baby sibling when he or she arrives - if the Cambridges keep up with tradition.
George visited newborn Charlotte a few hours after she was born in 2015, arriving with his father, the Duke of Cambridge.
The 21-month-old slightly nervous looking youngster was carried up the steps to the private hospital by William, and gave the crowds a small wave.
George, dressed in blue shorts, a white collared shirt, a blue pullover, long blue socks and black bar shoes, was given a reassuring a kiss on the forehead by the duke.
More than 30 years earlier, two-year-old William held hands with his father, the Prince of Wales, as he entered the hospital in Paddington, London, to see his mother, the Princess of Wales. and one-day-old Prince Harry early on September 16 1984.
The newspapers at the time reported how William, who was dressed in red shorts, a white shirt with red embroidery, white ankle socks and traditional leather bar shoes, ran down the corridor into Diana's arms as she called his name.
He was said to be "very, very excited about seeing his new brother".
The introduction was judged a success, with William holding baby Harry's hand as he lay in his cot.
He spent 20 minutes at the hospital before waving to the crowds as he was taken home by his nanny, Barbara Barnes.
While four-year-old George has already experienced adjusting to a sibling, it will be Charlotte, who is nearly three, who will need to get used to no longer being the baby of the family.
Parenting site madeformums.com offers advice on ensuring first meetings go well.
"Make sure you are not holding the new baby when your toddler first sees you after the birth," it said.
"Give your toddler a big hug first, then introduce her to the new baby after a few minutes.
"Buying a present for the new baby to give to his or her older sibling may help."