There is an option to combine people at one address to get just one printed label, but this is no good for us as we have congregation members living in the same old person's home who should all get an individual mailing. What we really want is only to get combined labels when the members are linked by a relationship. Is there any way of adjusting the mailing label printer to do this without artificially messing around with the mailing addresses to avoid duplicates for the old person's home?
If you use households and have the spouses, children also have a relationship of member of household or head of household, then the check box "Merge labels for contacts belonging to the same household" will do what you want.
You could create two mailings one for people with a relationship and one for people without.
Use the relationship report to find all the people with relationships. Add them to a group.
Create another group with all the people in the congregation.
Then use the Search => Custom Search => Include / Exclude Contacts in a Group / Tag. You would include the group with all the people and exclude the ones with relationship. This will give you a list of congregation members who don't have a relationship. Create mailing labels for them without checking any boxes.
Then pull up the group of people with relationships and create labels for them checking combine addresses.
The downsides of this approach is every time you do a mailing you'll have to empty the groups and repopulate them.