Can i invite someone to my single player world? If so, How? [duplicate]

You can set up a local multiplayer server that uses your single player world as the world. Basically, what you do is copy the files in your single player folder over for the server to use. There's a little bit of set up needed. Here's a walkthrough:

A multiplayer server is the only way for two players to exist in the same world.

Even if you set up a server for your world, however, neither you nor your brother will be able to bring items into or out of that world, as your character's inventory is not shared between worlds/servers.

It sounds as if you may be familiar with Terraria's world/character system, which allows characters to switch between worlds at will and worlds to be opened in single- or multiplayer mode. Minecraft doesn't follow the same model; the closest you can get would be to spawn some diamonds in your brother's world (via mod or inventory editor) and destroy the same number in yours (say, by tossing them into lava).