LAN duplication glitch

Put the summary of the bug you're having here

What I expected to happen was...:
when i opened to lan and opened another launcher, and got my freind to log on and join lan, on my computer(two launchers, one computer) i expected him to have a fresh inventory and be at spawn.

What actually happened was...:
when i open to lan so i can get my freind to me i opened another minecraft launcher, got him to log in as his charachter and i got him onto LAN when he came on, he was standing where i was, and he had my inventory, so when we logged him off, my computer and he went on his, he still had my inventory.

Steps to Reproduce:
1. open up a lan
2. open up a second minecraft launcher
3. go onto the lan world logged on as a different person, ON THE SAME COMPUTER