The Tim Ar-O (TO) languages are, I think, one of the high points of my conlanging career. Much like Mark Rosenfelder did with Proto-Western, I took two of my conlangs and worked backwards from them to produce a unified source. This feat may be somewhat less impressive than it sounds as the primary load-bearing member of the language family is Classical Ĝare n Tim Ar (CT) as opposed to O (or Proto-O), so it takes precedence over any existing canon in O for terms of comparative vocabulary. That said, O has left its mark on the language--primarily with regards to the pronouns.
The impetus for unifying the two into a single macrofamily was simple; I noticed that there were similarities in the genitive constructions in CT and in O--in CT, the default form of the genitive particle is n; in O, the prefix n- is the prevocalic form of the genitive in that language. From there, I attempted to work backwards to arrive at something consistent with the phonologies and morphologies of both languages.
I've gone through multiple iterations of sound change paradigms for both, in an attempt to keep things consistent with established canon, primarily as there are several sines qua non--namely, I was dead set on the exact phonologies of both languages. This was particularly troublesome in the case of O, wherein the language was designed to have only eight phonemes. The result is a situation I like to compare to that of Indo-European: In terms of development from the protolanguage, CT is akin to Lithuanian; O, to Tocharian.
The Beheic languages are those languages that come from Beheic stock. Genetic and linguistic evidence suggest that the Proto-Beheic language was originally spoken in the central and southern Burning Mountains in approximately the early III &en; IV M BC. Most of the proto-Beheic contingent appears to have migrated westward and to the north, inhabiting the wide strip of land north of the range, though a few smaller communities ventured south. Various clades subclades of languages split off from this common ancestor, and the Tim Ar-O (TO) languages are by far the most successful of the Beheic languages, with Classical Ĝare n Tim Ar (CT) being the official language of the Tim Ar Empire.