"It is you." is correct in English for both singular and plural "you". You could say "It is them." and "It is us." in response to "Who is it?" (at the door) "Who" and "it" are singular though unknown person place holders that could turn out to be holding the place for more than one person at the end of the answering sentence.
Sounded like "De har jer".
Sound comparison: https://translate.google.com/#da/en/De%20har%20jer.%0A%0ADet%20er%20jer.