When selecting names for your characters, you can of course borrow and adapt names from famous people, especially if those particular names will be a good fit for the person in your story. However, you’d be unwise to use a name that will be too familiar to people and make them immediately think of a particular historical person, who may or may not have anything in common with this fictional person you’ve created. Even if Roosevelt or Churchill are heroes of yours, unless the narrative is related to them, it might be best to avoid these names and use something else. It could be similar sounding, but don’t go for an exact copy. Also, even an adapted name could spell trouble if you decided to use the name Bradley Pitt or Thomas Cruise for your hero, since they are clearly identified with real people.
Even with secondary characters, avoid names that are too similar or even just start with the same letter. For example, if you had a liking for J names, calling your characters Joanna, Justin, James, Josephine and Julia will serve to confuse the reader. These are all good strong names and valid for any story, but not in the same novel. Even steer away from having heroes and villains with similar names, especially when there are so many names in the world to choose from. If your hero is called John, why called the villain Johnson? And many writing tipsters will tell you to avoid transgender names for the key characters in the same story. If your heroine is Samantha or Patricia, don’t call the hero Patrick or Samuel, since these names are all abbreviated in the same way. Even if the heroine is Jamie and the hero Chris, this can cause the reader to become confused, lost or just disinterested and put the book down, which is the last thing you want to happen.