Q: My family has two iphones, which unfortunately got signed up under the same icloud account.  We are now getting eachother's calls and texts.  I'm afraid to totally delete my son's phone off of this account.  How can I change this?

Calls on two phones:

Partial solution:

Open Settings on both iPhones, then choose “FaceTime”

Toggle the switch for “iPhone Cellular Calls” to the OFF position on both phones.

http://osxdaily.com/2014/12/15/different-iphone-numbers-ringing-same-time/

Best solution by far <<<

Get separate Apple IDs and use Family Sharing.

https://support.apple.com/en-us/HT201088

Settings > Phone > Calls on Other Devices > Allow Calls on Other Devices > Toggle Off

Settings > Messages > Send & Recieved At > Uncheck any number/mail that does not belong to the device

Settings > Messages > Text Message Forwarding > Toggle All Devices Off