Households are made up of a wide-variety of related and semi-related people. Families do not all live in the same household.

I really need a way to connect people directly as relatives who live in different households (especially for children in a split marriage, but also for two post-retirement sisters with different last names that anyone not entrenched in the system wouldn't know they are family).

In the "Family" section of an individual, simply make a heading "Household" and include everything already connected in there, then make a heading "Additional Family" where you can connect them via the same relationship options to other people outside the household.