Nobody's Boy

Rémi learns that those he thought were his parents are not, but are instead people who took in a child who was found abandoned. His foster father decides to send Rémi off into the world with a traveling musician Vitalis for money. Rémi finds Vitalis is a good master and he learns much from him.

I can easily see why this is one of the 1001 Children's Books You Must Read. It's a fantastic story of loss and love and learning and life.