"Grandmother is in our house."

Translation: नानी हमारे घर में हैं।

[jewel.james]

Why is oblique case used here?

[Zerenei]

Because घर is followed by में, postpositions like में change how you refer to the noun into the oblique case.

[PKpraveenK]

Difference between hamara ;hamari;hamare and where to use them

[DennisLDuolingo]

हमारा: masculine singular. हमारे: masculine plural, oblique case, formal. हमारी: feminine.

[Tamil360]

Why hamare? And not hamari?

[21deen]

...because it qualifies "ghar" which happens to be in oblique case.