"जूलिया के पिता गरम दूध पी रहे हैं।"

Translation: Julia's father is drinking hot milk.

[Pacific_Brent]

Why is it /rahe haim/? If the subject is a singular masculine noun?

[zeebo7]

Julia's father is being referred to respectfully, hence why we use रहे and हैं (with the anuswar).

[AlanPierce5]

See the "Formality and Respect" section in the Family Tips and Notes:

In formal situations and for respected people (including all elders), plural versions are used in every context. For example, with पिता (father): मेरे पिता भारत में हैं - My father is in India; उसके पिता अमेरिका से नहीं हैं - His father is not from America.

[OJFord]

Those examples are in the oblique case anyway, so the only way you can tell they're plural is from the ं in हैं।

[Prya_hindi]

I did not see any tips in this duolingo course...
And your link does not work for me.

[OJFord]

To agree with के, which is used to show more respect than with का।

[DavidONeil4]

I have trouble knowing whether the English should be "drinks" or "is drinking" (same with other verbs). Is there a general rule that can be briefly summarised by some kind person here? Don't worry if not possible. I can look it up in the tips (or elsewhere) when not using my mobile. Thanks in advance if possible!