Why is my phone ringing when someone calls my husbands phone? The number shows up on my phone and says "from your iPhone".
Both of your phones seem to be connected to the same iCloud account.
In iOS 8, one iOS device can answer another device's phone calls and vice versa. This feature is called Continuity.
Take a look here for more details: https://www.apple.com/ios/whats-new/continuity/
I was having the same trouble. Cathalog is correct, this is a new "continuity" feature in iOS8.
Go to Settings > FaceTime, there is a slider labeled "iPhone Cellular Calls":
Use your iPhone cellular connection to make and receive calls on devices signed into your iCloud account when they are nearby and on Wi-Fi.
Turn this slider off, and it should disable this feature.