And royal baby No. 2 makes four!
Over the night Kate Middleton and Prince William welcomed a baby daughter, giving son Prince George an adorable little sister. The famous couple even debuted their baby girl on the steps of the Lindo Wing in London (how cute is she?!)
While little George isn't even two years old yet, we bet he'll be the best big brother any princess has ever had!
In celebration of the Duchess' birth, check out more famous celebrity siblings.
Tune in for a brand-new episode of The Royals this Sunday at 10 p.m. on E!