The whole royal-surname business is a complicated one.

Way back when Prince William and Prince Harry started school, Princess Diana and Charles decided they wanted their kids to live a more normal life, so they decided to give their children the surname 'Wales' so they could fit in. It was probably more Diana's doing, as she wanted her kids to have regular childhoods, where she would bring them out to theme parks and play areas even if it went against royal protocol. When Prince George started school last year, William and Kate followed suit and decided to call their son George Cambridge, as they are Duke and Duchess of Cambridge. We're presuming Charlotte and Louis will also take up the surname... and it means that Meghan and Harry's kids will have a different second name to their cousins too. We very much doubt that Meghan and Harry will want to be acutely royal when they have children, so will probably go along with Diana, and Kate and William's decision, making their kids' surnames Sussex. They will no doubt be absolutely adorable and we'd say Harry will break even more royal protocol with them as he and Meghan seem more down to earth, but it'll be interesting to find out all the same.