That is crazy. I was thinking he was 12 or something too. (⊙…⊙ )
he is twelve, well now thirteen.
http://iweb6.mangapicgallery.com/r/newpiclink/soredemo_sekai_ha_utsukushii/41/1c92751a2bc6ede87d22ac9ae3f791da.png
Well this site says otherwise
http://soredemo-sekai-wa-utsukushii.wikia.com/wiki/Livius_I
* forget to say: "read the Trivia" @.@ really confusing 12 > 13 or 15 > 16
I notice that they mention that this is according to the anime. They may have been forced to say his age was 15/16 in the anime due to recent changes in laws when it comes to depicting "relations" in anime in japan. About 4(?) years ago they slowly started cracking down on child pornography and maybe to skirt the entire issue, they just say he's a really tiny 15/16 year old. Manga is not so strictly enforced.
Another possibility is that the wikia is just wrong. Not unknown to happen in a crowd sourced article.
2 years ago evidently: http://time.com/2892728/japan-finally-bans-child-pornography/
At 1st I was confused 'bout Livi and Nike age difference. And reading the comments made it seems they got a hugh age gap. But in fact they just 1 year apart. Livi being 16 yro and Nike 17 yro (red it in wikia) I thought Livi was 12 and Nike 19 or something (￣∇￣")