Every time I send a text to my sons iPhone I get a copy of it sent back to me in a separate text

You should try rebooting your phone. If that doesnt work, do a factory restore from iTunes.

Go to settings, messages, Send & Receive, uncheck any phone numbers you don't want it sent to (this changed after we updated OS)

Go to settings, messages, Send & Receive, uncheck any phone numbers you don't want it sent to (this changed after we updated OS)

Go to settings, messages, Send & Receive, uncheck any phone numbers you don't want it sent to (this changed after we updated OS)