When to use the nominative and the accusative?

Question

There are five people in my family. My grandparents, father, mother and I. My mother is a nurse. My father is a teacher. My grandparents were retired many years ago. My grandma was a dancer. My grandpa was a driver. But he is learning English now. I have a happy family.

I think the sentence above is an elliptical sentence, and the complete sentence should be: (They are) my grandparents, father, mother and I.

"my grandparents, father, mother and I " is a complement, but "I" is a nominative, how can it be used here?

I wonder when to use the nominative and the accusative.

Answer 1

"There is" ("there are") is used to indicate that something exists. It is very often used in descriptions. It is correct in the sentence you give "they are" would not be correct.

There are five people in my family.

In your paragraph the sentence serves as introduction to the description that give details of the five people.

My grandparents, father, mother and I.

represent the five people in the introductory sentence, where they are all subject^* of the verb "are". So "grandparents", "father", "mother" and "I" can be seen as having a subject form. A more probable punctuation would be to have a colon (:) instead of a full stop (.) to separate the two sentences.

But saying:

My grandparents, father, mother and me.

is correct as well and probably more common.

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^* In English we normally use subject and not nominative, object and not accusative.