It is supposed to be working together on a project. So forcing you?
Something similar only happened to me once when I was working at a new business (this was when only the last 3 versions were supported). We just agreed that we would supply ifc and nwd files so that they could be used in the project.
Now with the 5 version support and almost everybody on subscription the chances of running into these issues will be a lot smaller. And with years progressing you can backup older family libraries. The only time you might see something in older versions is in already long running projects. Even there I expect at a certain time they will upgrade (to be sue they are supported by Autodesk).
You also can point out that you might probably not be eligible to use these older versions.
So personally I would not worry about it, enough options. They can upgrade to a newer version or you can supply other formats allowing the project to progress (ifc, nwd). Just discuss before starting the project.
So make your libraries in the oldest supported version.
Or in newer versions if you not expext that the older versions are used by your partners. At the moment I see most projects in 2020 with some on 2019, I have not seen 2018 for some time now.
Louis

Please mention Revit version, especially when uploading Revit files.