@Sam9640 In Samsung calendar it looks like Invitee only appears if the event is being saved on a compatible calendar. When you create an event, you can choose the calendar that it is being saved to. On a new event dialog, it is immediately after the "Location" field.
For example, in the Select Calendar dialog:
- Choosing "My calendars" under "My Phone" does NOT show invitee.
- Choosing "Samsung Calendar" under "Samsung account" does NOT show invitee.
- Choosing any calendar under any of my Gmail accounts does show invitee.
See if this is why your husband isn't see the invitee field on an event.