There’s an official sound track found here: https://ackkstudios.bandcamp.com/album/two-brothers-official-soundtrack But more or less, required to buy. Though I don’t mind, some of them were identical from the actual game.
But I feel it sounds different from the actual gameplay of it originally. For example, the over world theme in game is different from the official sound track. Would be as happy as a cat if someone can search for the rest of the missing sound tracks of the actual game.