A Door Into Hindi: Lesson 15

If we don't know the gender or number of a noun or pronoun, it is assumed to be third person masculine singular.

Examples:

A.  कल आपके घर कौन आ रहा है?

 कल मेरे घर मेरी बहिन आ रही हैं।

 Who is coming to your house tomorrow?

 Tomorrow my sister is coming to my house.

B. कल आपके घर कौन आया था?

 कल मेरे घर मेरी सास अई थीं।

 Who came to your house yesterday?

 Yesterday my mother in law came to my house.

See Snell's Teach Yourself Hindi (2000) Section