My Friends tab is missing from my “Find My” app...

That is strange.

And KaeBFly, I was just going by what I have read. I don't have a Family Sharing plan.

And Cyberski, at this point the only thing that I can recommend is to create a current backup of the device and the restore from that backup. If that does not change it, then restore to factory, setting up as a new device. Sign into Apple ID and iCloud and see if the app changes. If it works, then try restoring your backup and see if it disappears. If it does, then it is something in your backup. Check to see if you have an Restrictions turned on in Screen Time.

If you have Family Sharing on, then those family members show up in Devices now, instead of People in the new app. If your older son is not appearing, have him check his device about sharing location.

Do you currently have someone that was listed in Find My Friends? You should be seeing an icon People. You can try force closing the app then open it again and see if that makes a difference.

Are you in a Family Sharing group? If so, that would explain the change.

I am in a family sharing group and I still have my people tab (all family members show on it too as well as on the devices tab) so I’m not sure this is completely accurate.