14w30c LAN world issue

When my brother connected to my lan world chat said
Dr_Dog789 joined the game
Dr_Dog789 joined the game
Dr_Dog789 joined the game
Dr_Dog789 left the game

But instead of just having one entity two Dr_Dog789 entities displayed, and the world wouldn't load on his computer, and he was unable to move the character, The short distance he could move the other entity would follow.

Steps for possible reproduction of this issue
1. Create a lan world, this was creative and superflat
2. Have someone else join the game!
3. Bathe in the amazing bugginess

Attached are some photos of the issue with displaying multiple characters and a picture of after killing himself the death entity still in place, the first 8 are just the multiple glitch and the last one shows the entity remaining after its death.