The Syriac Vulgate of the New Testament (Peshitta) appeared before the Fourth Century, and appears to shed some light that "the savior Jesus Christ" and "the great God" were appositive phrases.
The verse appears as follows:
Titus 2:13 (Syriac Vulgate)
The word for "glory" (highlighted in yellow above) possesses the third person singular suffix. We can compare with Kiraz (2003) as follows:
The words that follow the word for "glory" are all emphatic, which means they are definite. The words "Jesus Christ" are modified by the adjective for savior, which is emphatic.
In other words, all the nouns/adjectives following the word for "glory" are in the emphatic case; the masculine singular suffix to the noun for "glory" is in the third person masculine singular (and thus referring to the "glory" of one particular person); and finally, the phrase "and of our savior Jesus Christ" does not possess the indicator for the genitive case (ܕ), which suggests it is an appositive for the phrase immediately preceding, which is "of the great God."
In summary, the grammatical structure of this verse in the Peshitta suggests that the Syriac writers during the Fourth Century (or earlier) had taken the phrase "and of our savior Jesus Christ" in this verse to be an appositive for the phrase "of the great God."
Kiraz, George Anton (2003). Analytical Lexicon of the Syriac New Testament. Bellingham, WA: Logos Bible Software.