‘Children are being bred so an old rich man can use their hearts and live forever’: I’m on a mission to find the title of a book I read in school as a kid. Can you assist me in solving this mystery?

Hey there, looking for help with a book I remember reading as a kid. It’s a classic that’s often read by children, and it’s got quite the twist. So, picture this – there’s this kid living in a shed all alone in a field, completely isolated. Little does he know, he’s actually a clone, and in the future his heart is meant for an old rich man to live forever. Talk about a plot twist, right? Eventually, he escapes the shed, meets the old man, and learns the truth about his existence. It’s a real tearjerker, I tell you. I wish I could remember how it all ends, though.

Oh, and I believe the story is set in a Spanish-speaking country, which adds to the intrigue. Any thoughts on the title or author?