Players Invisible In Minecraft LAN

So I was playing Minecraft LAN with my cousin. I can see him no problem, but he can't see me. I tried to clear all my effects but it said I had none. I come over to his screen, and I can't be seen, even if he was looking straight at me. I tried to delete the contents of the playerdata folder, but that did nothing. Even if he applied the glowing effect on me. It did nothing.