Siri can't text someone even though it can call them, email them, and show me their contact information

Okay. I fixed the problem — at least so far.

Deleting the entry did nothing. I recreated the entry, it initially worked, and then failed five minutes later with the same problem.

On my iPhone, entries are "unified". For example, my wife has an entry for someone, and I have an entry for someone, it shows up on my iPhone as a single entry. On my iPad, these show up as multiple entries. If Facebook creates an entry, a third one shows up.

I want to my iPad, and there were three entries for this name — two had email and phone numbers and one did not.

Deleting that mysterious third entry worked for about two minutes, but it reappeared a minute later, and I had the same issue again. I ended up editing that third entry and added a phone number and email addresses. That allowed me to text John Smith through Siri. It so far has held for two days. I can once again text John Smith through Siri. However, other people who have Facebook profiles and are in my phone book aren't an issue. It was just this one.

Addendum

The problem was tracked down to Facebook being allowed to munge my address book. This user didn't have phone or email information in Facebook, so Siri must have seen the Facebook info, and tried to use that. On my iPhone, the contact entries are unified, so I see both what Facebook puts in and my entry.

Turning off Settings->Facebook->Contacts solved the issue.

There maybe similar issues with other contact applications like Twitter and Outlook which might cause Siri not to see the information you have for a contact. Turning off these app's ability to update your contacts may solve the issue.

My wife was having this exact problem with a few of her contacts (but just the ones she wanted to send text messages to the most). I found that I was having the same problem with several of my contacts. We both got new iPhone 7 Plus phones recently. I was finally able to solve this problem by getting Apple to delete the cache of data from each of our phones that Apple stores on its servers to process Siri requests (which includes the contacts from the phones). To get Apple's servers to delete the cache for your phone, do the following:

1. Open Settings, Siri, then turn Siri off.
2. If you get a warning that this will remove your information from Apple's server (and it will take some time to rebuild it if you later decide to enable Siri again), then skip to step 5.
3. If you get a note that says that Apple will keep your data on its servers to support dictation unless you also disable dictation, then you will need to disable dictation.
4. To Disable dictation, go to Settings, General, Keyboard, then scroll to the bottom and toggle "Enable Dictation" off. Now you should see the warning about your data being deleted from Apple's servers.
5. For good measure, turn your phone off (press and hold Power button until you get the "Slide to turn power off" message, then slide).
6. Turn your phone back on.
7. Go back to Settings, Siri, and turn Siri back on.
8. If you turned off Dictation, turn it back on.
9. Give your phone a few minutes to rebuild its cache of your data, then try Siri again. It should be working properly now.

This worked on both my phone and my wife's. I hope this is helpful to others that run into this problem.

Is the phone number you have for him labelled "Mobile" rather than "home" or work? That could possibly make a difference.