Translation:Are these the clothes of someone?
Are these clothes someone's? should be accepted.
Or, you could say: "Are these the clothes of someone else?"
It's kind of an awkward sentence in English altogether, but in Romanian, that would be "Hainele acestea sunt ale altcuiva?"
...But I'm not a native speaker, so someone can correct me :)
It accepts "Are these someone's clothes?", which is more natural, although I struggle to imagine the circumstances in which anyone would say that. "Whose clothes are these?" would be much more likely.
These the clothes? Really? The?