Copyright is held by the person who creates the work, not the person who owns the device (typewriter, camera, chisel). However, copyright may be held by the person who hired the creator to create the work, that is, the work may be a "work for hire". In the US, this refers to "a work prepared by an employee within the scope of his or her employment". As you describe it, this is not a work for hire. It is also possible that A might have a contract with B where B takes pictures for money and transfers copyright to A (presumably not applicable).
Copyright in pictures taken by the relative is held by the relative. Copyright in the pictures of the relative might be jointly held by the relative and the person operating the camera. The creative (protected) elements include not just the act of pressing the button, it includes all sorts of setup stuff. Then the relative and the other person may hold joint copyright in the work. Since copyright is about protecting a person's creative work and it is unclear whether the operator contributed creatively to the work, it's impossible to say whether certain of those pictures are "Copyright Relative and Anonymous". If I hand a person my camera and say "Take a picture of me", that doesn't constitute the kind of creativity on my part that is protected by copyright law (whereas a more detailed description of what should be the camera angle relative to the rock and the sun etc. would involve requisite creativity). Lacking any substantive information on how the picture was created, it is hard to assert with confidence who holds copyright.
In the 19th century, the U.S. Supreme Court clarified the photographer as owner of the photograph in Burrow-Giles Lithographic Co. v. Sarony, 111 U.S. 53 (1884).