Why can't the Princess Royal become queen?

Answer 1

I assume you mean Princess Anne. She could become queen, but only if her three brothers and all their children died first. I assume you mean Princess Anne. She could become queen, but only if her three brothers and all their children died first.

Answer 2

They are heirs to the throne, Andrew is 4th in line, Edward is 7th. However it is unlikely either of them will take the throne, as Charles' sons, William and Harry rank before them in the line of succession, and any children they have will push Edward and Andrew further back.

Answer 3

Marraige into the royal family does not usually grant the title prince or princess. Marrying the ruling queen will grant the the title of Prince Consort. Marrying the Prince of Wales will also carry the title of Princess of Wales to the wife, as was the case with Princess Diana, and also Camilla Parker-Bowles, though she chooses not to be known by that name.