If you are not sharing an Apple ID (or if you were, but the issue persists after following the steps in my previous reply), then next try the following steps, which have resolved similar issues for others:
- In the Contacts app on your iPhone:
- For each of your contacts who sends you Digital Touch messages:
- Check that there is a single contact card;
- Check that their card contains their iPhone number and Apple ID email address - and none of your own contact details.
- Check that there is a single contact card for you and that it contains your own Apple ID email address and your iPhone number - and none of anyone else's contact details.
- On your iPhone, go to: Settings > Mail, Contacts, Calendars > in the Contacts section, check that My Info is using your contact card.
- On your iPhone, go to: Settings > General > Siri > My Info - check that your contact card is selected.
- Check that you have added your preferred contacts to the Friends list on your Apple Watch using their contact cards:
On your iPhone, in the Watch app: My Watch > Friends.
- Via a web browser, sign in to Manage Your Apple ID: https://appleid.apple.com/
In the Account section, under Contactable At, check whether anyone else's iPhone number and/or email address(es) are listed - if they are, delete them.
- Delete old iMessage conversations with your contacts on each of your iPhone and Apple Watch:
- iPhone: Messages app > swipe left on a message thread > delete.
- Watch: open the Messages app (from the Home screen, which is accessed via single press on the Digital Crown) > swipe left on a message thread > tap on Trash / Delete.
- Set new Messages conversations to start from your iPhone's phone number:
iPhone: Settings > Messages > Send & Receive > scroll to Start New Conversations From > choose your iPhone phone number.
- Check the email addresses at which you can be reached via iMessage:
iPhone: Settings > Messages > Send & Receive > under You Can Be Reached by iMessage At > in addition to your iPhone number, enable (with a check mark) your Apple ID email address (do not enable any other email addresses that are not solely yours).
- On your iPhone in the Watch app: My Watch > General > Reset > tap once on Reset Sync Data:
- You will not see anything happen after tapping it (the process will run in the background, invisibly to you).
- Wait for a minute or so, to allow the process to complete.
- Disable and re-enable iMessage on your iPhone:
iPhone > Settings > iMessage > toggle off / on again.
- Restart both your iPhone and your watch (turn both off together, then restart your iPhone first):
To turn your watch off: press and hold the side button until you see the Power Off slider; drag it to turn off. To restart: press and hold the side button until you see the logo.
If the issue persists, ask any affected sender of Digital Touch messages to follow the equivalent process on their iPhone and watch.
More information:
Use Digital Touch - Apple Support