Player 2 logs into a single player world and receives the inventory and enderchest from player 1.

I expected Player 2 to have his own inventory and enderchest items.

How to recreate:

I have 2 minecraft accounts and play over a LAN with my son, where my single player world is on my computer and I log in as player 1, then I open the world to LAN.

My son joins in from another computer as player 2

Later, my son plays on my computer logs in as player 2 and joins the single player world. However, all of his inventory items are gone, and are replaced with inventory from player 1.

Apologies if this is a duplicate, I could not find it.