Writing a fiction story and turning it into a cohesive novel is hard work. It's something you create from nothing. Writing isn't just placing word after word on a blank page its looking at a blank page and developing scenes and dialogue. When you place a character's name on a page it's as though you created a new life. Believe it or not a character has a past, present and future place on the stage you create to tell your story. In the context of a story you may never meet a character's family, friends or acquaintances but they have them. An author always has them in mind if not on the pages of his story.
My new novel has a large cast of character's. It's complicated to track who is who sometimes. When I create a character I always complete a character profile. I know their religion or lack thereof. I know their politics and if they smoke or not. If they are in great shape or have a life threatening disease...and so on. As soon as I have a name for the character I write it on a yellow legal pad so I can track where they fall within the total cast of characters. The only other info I note on the legal pad list by their name is their age and what chapter number they first appear. The legal pad helps me keep on track with who is who within the emerging story.