It might be stupid question. I know that many people have only one lens, and that should be enough if you can master it. However, I think different lenses have different signature and capability, and so there are many people have more than one lens even in the same focal length.
If you are the one who has more than one lens in the same focal length, could you please advice which lenses you have. And if possible, the reason why you decide to have both (or all) of them.