Can you cite other master's theses when writing your own?
In general, there is no such widespread requirement or expectation anywhere in academia. (Perhaps a particularly unusual advisor might have such an expectation, but even then, I doubt it.)

If you note the citations of research papers, a decent number of them will cite master's theses—some of my papers certainly do! And if I can submit a paper to a major journal that cites a master's thesis, why wouldn't another student's master's thesis?