Baby Girl Sussex is coming, so what’s big bro Archie to do?

FILE - Britain's Prince Harry and Meghan, Duchess of Sussex, pose with their newborn son Archie Harrison Mountbatten-Windsor in St George's Hall at Windsor Castle, Windsor, south England, on May 8, 2019. It won't be long before Archie is a big brother. His mother is due to give birth to a baby girl sometime this summer. Hopefully, the introduction of the new sibling will go smoothly, but seasoned parents and pediatric experts warn that the transition takes preparation and diligence. (Dominic Lipinski/Pool via AP, File)
FILE - Britain's Prince Harry and Meghan, Duchess of Sussex, pose with their newborn son Archie Harrison Mountbatten-Windsor in St George's Hall at Windsor Castle, Windsor, south England, on May 8, 2019. It won't be long before Archie is a big brother. His mother is due to give birth to a baby girl sometime this summer. Hopefully, the introduction of the new sibling will go smoothly, but seasoned parents and pediatric experts warn that the transition takes preparation and diligence. (Dominic Lipinski/Pool via AP, File)

NEW YORK – Archie Harrison Mountbatten-Windsor, the 2-year-old son of Prince Harry and Duchess Meghan, will soon have a sister in the California hamlet the decamped royals call home.

Hopefully, the introduction of Baby Girl Sussex in Montecito will go smoothly for the toddler, but seasoned parents and pediatric experts warn that for any family, the transition takes preparation and diligence. Throw in the upheaval of a pandemic for extra challenges that can include toilet regression, sleep strikes and aggressive behavior.

Fear not. There are myriad ways to help make the introduction of siblings as smooth as possible.

For starters, mom-of-two Morgan Ball advised: Try to take it all in stride.

“Hope for the best and plan for the worst,” said the 34-year-old Ball in suburban Columbus, Ohio. “Don't freak out about it. Kids have big feelings. They do weird things. They might bite their baby brother and that does not mean they're going to be a serial killer.”

Ball's oldest was 3 when his brother was born in April 2020 as pandemic panic took hold. To make matters worse, her husband's father had died suddenly not long before, further rocking young Charlie's world.

“I'm sure there's a lot of people who could tell a similar story because they lost someone during COVID," she said. “It's been tough in terms of his behavior. It took a lot of understanding."

Ball and her husband knew about the usual suggestions to prepare Charlie, including reading him books about babies and new siblings, letting him pick out a gift for his new brother and giving him a baby doll.