Life as a royal can consist of a decent amount of traveling; in a pre-pandemic world, working royals would go on elaborate tours of foreign countries to represent the crown, so it comes as no surprise that royal family members speak more than one language. As noted by Express, Prince William speaks English (of course), German, French, and Gaelic, and it looks as though his children are following in his multilingual pursuits.
According to People, Princess Charlotte, even though she's so young, speaks some Spanish. Her nanny, Maria Turrion Borrallo, is originally from Spain and has been teaching Charlotte the language. She also attends the Willcocks Nursery School, chosen by her parents due to the impressive team of educators, which no doubt is helping her along with her linguistic skills.
Charlotte's older brother, Prince George, also speaks some Spanish. As noted by Reader's Digest, could count the numbers up to ten in the language by the time he was 4 years old. If they're anything like their dad, the Cambridge children will be multilingual before they know it.