In the UK, there are several specific rules that explain which members of the Royal Family are entitled to hold a prince or princess title.
Many of these rules date from Letters Patent by King George V in 1917, where he wrote that all the children of the sovereign, the male-line grandchildren and the Prince of Wales’s eldest son were all allowed to hold a princely title.
While Princess Beatrice and Princess Eugenie both have titles as they are male-line granddaughters of the late Queen, their children are not entitled to become a Prince or Princess.
However, this is not to say that they aren't eligible to hold other aristocratic titles in other countries. Both of the York Princesses have children.
Read more on ok.co.uk