Baltic languages
Lithuanian is one of two living Baltic languages, along with Latvian, and they constitute the eastern branch of Baltic languages family. An earlier Baltic language, Old Prussian, was extinct by the 18th century; the other Western Baltic languages, Curonian and Sudovian, became extinct earlier. Some theories, such as that of Jānis Endzelīns, considered that the Baltic languages form their own distinct branch of the family of Indo-European languages. There is also an opinion that suggests the union of Baltic and Slavic languages into a distinct sub-family of Balto-Slavic languages amongst the Indo-European family of languages. Such an opinion was first represented by the likes of August Schleicher, and to a certain extent, Antoine Meillet. Endzelīns thought that the similarity between Baltic and Slavic was explicable through language contact while Schleicher, Meillet and others argued for a genetic kinship between the two families.