I'm confused -- is तुम plural as well? In other words, can "tum" be used for "you", when "you" is more than one person?
Yes, but it's usually followed by लोग as in तुम लोग when used as plural, I think. As in you lot, y'all, or you people. English has the same "problem". It's pretty darn confusing for other people.
Just like english, yes. "Are you siblings?" You-plural.
How is on hindi Do you have siblings?
someone please answer this guy
How is in hondi Do you have siblings?