"Oriental" languages is not a linguistic classification the way Romance languages are. I assume you're referring to Japanese, Chinese, and Korean? Japanese and Chinese are themselves actually considered multiple language by linguists. There is a hypothesis that Japanese, Korean, Turkic, and a few other language groups should be lumped together as the "Altaic" group, but it's not a commonly held hypothesis among linguists anymore.

There are, however, a large number of loanwords shared among Korean, Chinese, and Japanese, as is fairly common for languages in contact with each other over a long period of time. Establishing a genetic language relationship depends on demonstrating a related vocabulary, particularly for the most commonly used words. This is done by establishing a set of regular sound changes by which you can show how two languages' vocabularies come from the same origin. Linguists do the same with grammars.

You may want to ask this on /r/linguistics, particularly their Q&A thread.