Why did a seven year old agree to marriage?

We all know many versions of Snow White. In most versions she is under the age of ten. In Disney she is a little older, about fourteen. In every version she agrees to marry someone she barely knew. Why would a young girl agree to marry someone she doesn't know? And why would a young man propose marriage to a child? If you knew Prince Florian the way I do, that would all make sense. To see and read his story for free please go to Smashwords and type in "Prince Florian".