Classification
Wittmann (1991) posits that LIBRAS is a language isolate (a 'prototype' sign language), though one developed through stimulus diffusion from an existing sign language, likely Portuguese Sign Language and/or French Sign Language.
Nevertheless, autochthonous sign languages flourished among Brazil's Indigenous peoples (that perhaps influenced Libras to some degree), and it shows similarities with members of the French Sign Language family.
Read more about this topic: Brazilian Sign Language