Which is correct??

[ongetz]

Which sentence is correct?

a. I went to my father's mother's house.
b. I went to my father mother's house.

[Soup]

a. I went to my father's mother's house.
b. I went to my father mother's house.

[ongetz]

Could you pls. give me more notes about this rule?

Thanks...

[Soup]

a. I went to my father's mother's house.
b. I went to my father mother's house.

In a., above, there are two possessive phrases:

1. father's mother <his monther>
2. mother's house <her house>

In joining the two phrases together, you need to omit the redundant word (note that, mother occurs twice, so one of those nouns is omit) and we get,

father's mother's house