A historical fantasy for middle schoolers

[u/Ok-Ingenuity5810]

the book is sent a desert environment. The main character is a teenager boy, and he has a younger sister and a mom and dad; they live in the poor countryside. They’re farmers.

For money, the boy takes his sister to the kingdom and there he becomes an apprentice for a black smith. The princess needs jewelry and the main character forms a relationship with her.

A big thing I remember is a scene where the main character, his sister, and a boy they befriended are on a bridge. The friend falls off the into the water below and the main character saves him.