What is a concise word or term for the cognitive ability to passively gather and recall personal minutiae about other people in one's life?

Solution 1:

According to Wikipedia, there are four main categories of autobiographical memory, one of which is this:

Biographical or Personal: These autobiographical memories often contain biographical information, such as where one was born or the names of one's parents.

On this basis, you might want to consider the term biographical memory, which would encompass a wide range of personal minutia about other people in one's life. From Lexico:

biographical: (of data or a written work) dealing with a particular person's life.

One's biographical memory could range anywhere from excellent to poor.