why is plural हैं here if पिता is singular? I think that was explained somewhere, but I don't know where to find it.
It is a way of giving respect/being formal. Words referring to older people or people who are in a higher position (like पिता, दादी, गुरु etc) are generally treated as if they were plural.
I suspected as much. Thank you for clearing that up so quickly. It's a bit like European languages that use plural second person to address single people politely. Or kings referring to themselves in the first person plural.
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