I have a problem. I want to name a character (the main character's romantic interest) Tobias, but I feel like people would associate him with Tobias Eaton from Divergent, knowing how much I love that series. Even before Divergent came out, I adored that name, along with Miles and Christopher. I don't want to use the other two, because they don't fit the character. I'm so confused on what to do...
If your book is dissimilar enough from Roth's that it does not remind readers of her series, there is no problem if you use the same name. Her's wasn't the first time that name has been used in fiction, either.
If on the other hand you are writing a Young Adult dystopia where teens have to undergo life or death trials and fight the rulers, you might want to make the name as dissimilar as possible so as not to appear as too much of a rip off.
Finally, I wouldn't worry about the name too much, you can always change it after you finished the manuscript. In fact publishers sometimes ask for a name change. So just use whatever name you like during writing and then approach that question after you have received alpha reader feedback.
Ditto What: I have never read anything by Veronica Roth, but if you're writing a story that is similar to her books, AND the characters have the same names, then yes, that looks like you're copying. If the story is nothing at all the same, if her books are "young adult dystopia" (as What indicates) and yours are historical romances for senior citizens, the fact that a character has the same first name would probably not even be noticed. I'm sure there are lots of books with characters named "John" or "Sally". :-) At least, as long as the name isn't made up or extremely rare. If you wrote a book with a character named "Darth Vader" or "Dumbledore", people would notice. But "Tobias" is a real name that real people have.
That said, you talk as if the only possible names for your character are Tobias, Miles, and Christopher. There are thousands, maybe millions, of names out there. Get a baby name book, or look up a list of common names on the web. If you think there's even a small chance that this name will cause you trouble, there are plenty of other possibilities.
I think of Tobias from Arrested Development. I think enough people have a variety of Tobias examples that it may not immediately link to the other guy.
If that is a worry, think about what part of the name you like -- is it the rhythm, links to what the name historically means, the strong 2nd syllable, starting with the "T" or the "Oh" early on? That it's a biblical name? Playing with Naming Dictionaries may help you come up with some alternatives that match some of those characteristics.