Outdated Servers Unable to Access World
Solution 1:
If only one of you has the latest update(0.14.1), it is a version error. Check the App Store to confirm you have the latest version.
Your brother's iPad air and your iPad 2 both have 0.14.1, because the message says outdated server with your brother's iPad 2.
So, to fix this, simply update Minecraft.
If that doesn't work, go here:https://blogs.windows.com/devices/2015/09/18/how-to-play-multiplayer-minecraft-pocket-edition/.