Can I add something? It may be helpful, and I think it goes to the spirit of your question.
In instances where, when Individual X is checked, a nexus--a criminal nexus or some sort of clear criminal association with someone else--comes up in the course of checking him or her, if that person happens to be a spouse or happens to be a brother-in-law or happens to be a lover or happens to be who knows what, then that is reflected in that person's background check.