Baby Sussex's name is yet to be announced to the public as it is custom to wait for the Queen to be informed of the name by the parents. Back in April, it took Kate Middleton and Prince William four days to announce Prince Loui's name, so we may be in for a bit of a wait!
The Duke and Duchess of Cambridge have taken a page from the Sussex book on social media and decided their first public congratulation's to the new parents would be via an Instagram post.
WATCH! Beaming Prince Harry speaks after the birth of a royal baby boy
Reposting the Duke and Duchess of Sussex official announcement, Kate Middleton and Prince William wrote their own special well-wishes to the first time parents.