Prince Hans has twelve older brothers. In Frozen, that makes Hans the thirteenth son in the succession order of the Southern Isles and helps explain why he views marriage into Arendelle as a path to power.
Hans arrives in Arendelle for Elsa’s coronation and quickly presents himself as a charming, attentive prince. He proposes to Anna after knowing her for only a short time, and she accepts. His apparent romance is later revealed to be a calculated scheme: he intends to marry Anna, arrange Elsa’s death, and take control of Arendelle.
The large number of older brothers is not just a joke about Hans’s family. It gives his ambition a political motive. As thirteenth in line, he has little realistic chance of inheriting the Southern Isles, so becoming king elsewhere appears attractive to him.
Viewers sometimes confuse Hans’s twelve older brothers with the number of princes seen on screen. The film does not introduce all of them individually; the count is given as part of Hans’s character background. His punishment after the failed coup is also said to come from those older brothers.