My wife and I both have individual Dropbox Plus plans, and we've thought about consolidating to a Family plan, but we don't see the benefit in paying 70% more for 50% of the space. (It works out to $60/TB-year with what we've got now, vs. $102/TB-year if we were to convert.) It seems to make sense to just create a shared folder, but what happens to the data in a shared folder if the account holder who created the account dies or becomes incapacitated and the account isn't renewed?
That sort of helps. Reading between the lines, as long as my family has access to the cached local copies of my files, they've got the data. If I'm not syncing all of the data, though, it's not clear whether Dropbox would be able to recover the data from the cloud if my account expired for non-payment. (Based on past experience, things can drop through the cracks after a family member expires.)