Charlotte, who turned 4 Thursday, is the royal couple's middle child, between 5-year-old Prince George and 1-year-old Prince Louis. She is fourth in the line of succession for the British throne, after her grandfather, Prince Charles; her father, William; and her brother George.
Prince Harry and his wife Meghan, who are awaiting the birth of their first child, wished their niece a happy birthday on Instagram. Responding to a Kensington Palace post featuring Charlotte's photos, they wrote: "Happy Birthday Charlotte! Lots of love, H and M xo."