As someone who has had many readings, as a client of my medium, with souls of dearly departed and my spirit guides, I can add some perspective from my experience. It seems that who shows up often has to do with what my guides perceive as my needs. It can also be driven by the needs of the soul of the departed. There have been instances that we were told that whom I wanted to speak with was not being made available by her guides when, as an example, she was deep in her life review. My guides never left me empty handed though. At least one and usually more of my five would always be present so that I got something out of the reading.