I read this book (might have also been more than one) as a teenager around 2010, borrowed from a local German library. I only very vaguely remember it. It was in German obviously but most likely translated from English.
IIRC the book takes place in a post-apocalyptic world where only different kinds of "clones"are left. Though I don't think "clones" of the same type had identical faces they just shared the same physical and mental traits and capabilities. Specifically I remember that the protagonist was of a line of weaker and smaller clones. This line although not as athletic or strong was very durable though (and maybe closest to humans?). So I'm a little hesitant to actually call them outright clones.
I remember a scene where he had to run from a stronger more brutish kind of clone, which ended in a room where he thought that the protagonist had jumped out the higher story opened window. He believed that because he knew how hard to kill these kinds of clones are and that he wouldn't die from that. (I think in reality the protagonist hid in the closet but I'm not 100% sure).
I don't remember the overarching story, but I believe the clones lived in the ruins of human society. I think humanity might have died out due to sterility, however the clones don't have extensive knowledge about this and the history is only hinted at. I think the (to my knowledge) protagonist travels with a female clone. I'm not sure if they are both teenagers or if I, as a teenager myself, projected that onto them. Clones have initially no concept of sex or reproduction and no interest in it, as far as I remember, and I don't know if the clones are even creating more clones or if that knowledge was lost as well. However these two develop some kind of love and at some point have a kind of more or less awkward "sex" scene where they discover their bodies and such.
I don't know if they have some kind of goal, if they're running from someone or what, and if they discover something great, like that not all humans are dead or something. I just know that the story and history of the world seemed very intriguing and revealed more and more as the story went on.
Edit: Clarification on the clones. I call them clones because they do not reproduce sexually, they are however not perfect copies of another human. They also are not normal humans in other regards. The protagonist was from a "line" of "clones" that is a lot smaller than normal humans I believe, however they are very hard to kill and can survive a lot more damage than a normal human being would. There are other "lines" of "clones", some are taller and a lot stronger but dumber than the average human and similar things.
As far as I recall there was not a single human involved in the story.
I should also mention that this book might have been targeted at teens, thus it might not have been as widely known as other books mentioned on this site. This is why I probably haven't been able to find it.
Edit2: Now that I've read it somewhere, it is quite possible that this book did not have any adults in it. As in, no adults exist, or that the clones die before they reach adult hood or something along the lines.