This sentence initially sounds like impolite speech in English. It fails to distingish people from, say, "things" in a room. It would make sense if perhaps you were pointing to a photograph. It could be stated at the end of a series of questions in which context had already been established. However, this would not be the first question asked.
meh. was just pointing out that just because it is not used often does not make it incorrect... and anyways, this whole debate is redundant, as the only reason this phrase is there is that it is pointing out what the Hindi means, and it is completely okay in Hindi... *shrugs - just pointing it out
Without context, "who are these" is actually an insult in english. You would be referring to "these PEOPLE" as "things" and not people. It would be very disrespectful to address someone as a "thing" or "things". You would say "who are these guys/people/folks/guests/amazing people". Please dont ever refer to people as "this" or "these". It would be like calling someone a slave or property. Dont do it.