Would it but okay to have a painted turtle live with 2 just born Alligator Snapping Turtles, I'm already getting them but i just wanted to make sure. And my sister has an Alligator Snapper with a painted turtle and a red eared slider at her house and they love each other. My painted turtle is lonely and my friend has 14 babies so i thought it was a good opportunity to get him a couple friends.

A definite maybe. Turtles are individuals and vary a lot. The slider is possibly the most territorial of the bunch. You will reduce the chance of fighting if the tank is over-sized.

Turtles are not social animals and don't get lonely. They may fight to protect what they consider "their" space.

BTW, are you sure that you have alligator snappers and not common snappers available? Can you tell the difference? If not, email me a photo of a side view, showing the shell clearly.