Victoria Princess Royal
By Franz Xaver Winterhalter via Wikimedia Commons
"If royal tradition continues, baby Princess Charlotte of Cambridge could eventually be given the very special title of The Princess Royal. If so, she would be only the eighth princess to bear it over the course of the last 400 years. The title can only be given to the oldest daughter of the monarch--so her father William would have to be King--and it can only be held by one person at a time, so the current Princess Royal, Charlotte's great-aunt Anne would have to be deceased. It is not an automatic title. In fact two of the princesses who were eligible to receive it did not, probably because they were already married to foreign princes at the time that they became eligible upon the accessions of their fathers."