If you read about a person...say Sarah What if there is another Sarah in your book. Sarah is a popular name. In my school class we had 4 Sarah's .3 Richard's and 6 Andrew's I know about 10 Sarah's. Normal person know folk with normal names. Yes or No
In real life, I can distinguish between different Sarahs by their physical features, accent/voices, environment and social context. These are all cues my brain learns and then relies upon subconsciously to associate the appropriate memories, feelings and experience with the appropriate Sarah. This is a subconscious ability upon which we all rely to ensure our brains feed us the appropriate and correct information to tell us which Sarah we are thinking about/looking at/talking to. When reading a book about fictional characters, a reader doesn't have all of these cues to help them keep track of different people who share the same name. When reading, our biggest identifying signpost is the characters name. This is why most people advise not even using similar names (Tom and Tim, Allie and Ellie, etc) within a book because of the readers inevitable confusion. Just because something is realistic in life doesn't mean it should be in your book. The only exception would be if your piece is non-fiction and the instances about which you are writing do actually have people with the same name.
I have a few minor characters share names with other minor characters or a major character to emphasize that it's generic. Example: the main protagonist's friend Gazi has a dad named Nat, which is also the name of the protagonist's uncle, who plays a larger role. Gazi's last name, Arkaesi, is also very generic, and my characters employ it as a pseudonym a few times. (Gazi, though, is not a terribly common name.) I also have characters use Zahn as a pseudonym, but the only character whose name is actually Zahn is a relatively minor (but important) character who comes into play late in the novel and appears only in the first book.
Wait, there's one more: That literary leviathan of another time Dr. Zeuss I recall once had characters with identical forenames.. what were they? Erm, Thingy, yes they were both called Thingy–no, not Thingy—it's coming to me now. How could I forget, we're talking his defining Magnum Opus here too. How remiss of me. I've got it. The Cat in the Hat. Sub-starring
You can also introduce the character by their name and then add something unique about them. Going on into the story you use that unique thing to further distinguish the characters. For example, if you have two women by the name of Sarah, you can weave into your story that one of the women has big hair. From that point on, you find a way to bring in the hair when that Sarah is the one being mentioned. Or you begin to call her by a nickname that lets the reader know you're discussing the Sarah with the big hair.