Trying To Find Book From Childhood?

I remember this one book I read when in my childhood, and its driving me crazy that I can't remember what it was called. The storyline went like this:

A guy is a son of a lord, then the lords brother comes, throws the lord in the dungeon, and inherits his castle, but the guy hides the lords sword in a tree and escapes with his mother because the lords brother wants to kill them. Then they meet up with a farming family somewhere in the forest, and after a while the guy and the farmers son go to get king arthur to resolve his injustice.

Ring any bells? Seem familiar to anyone?

I'm actually literally ripping my hairs out, one by one because usually my memory is flawless but I can't remember the name of the book.