Q: My son is getting my texts when he signed into my Apple ID.  How can I remove my number from his phone under the Messages/Send

You're sharing apple id for imessage that's why.  Go back into the above settings and uncheck or remove the apple id.

then make him a new one for himself.

you can still share apps without using the same appleID using family sharing read more Set up Family Sharing - Apple Support

that happens to my iPhone, my 2 kids, iPad and macbook pro

heres what you do

Settings> Messages> Send and receive>

then for you your number will not be highlighted but your wifes will so just click on it and make sure the check mark isn't next to it and then on the bottom it says start new conversations from and make sure your number has the checkmark

** if you use FaceTime make sure the email isn't checked (if it is then when they FaceTime to your email all your devices that have FaceTime app will ring)

i have to do this every time we update

we each have our own iCloud email but for the apple id we use the same email, it keeps us linked yet our backups are separate

hope this helps