Which is it?

Not "I." You need "me."

Both are okay.

Things will never be the same between me and my sister anymore.

Regards

Why me

isn't it "my sister and I are going..."?

Hi,

You can't say "things will never be the same with my sister and I". It's wrong.

"Me" is an object here. Have a look at this example:

Give this book to me. You wouldn't say "give this book to I", would you?

The same happens here. Things will never be the same with my sister and me / with me and

my sister.

Regards

AnonymousWhy me

isn't it "my sister and I are going..."?

It's because the pronoun placed after the preposition, as an object of the preposition, is always in the objective case: of him and her; with him and her. In other words, it is like saying: of him and of her; with him and with her. The only case when one can put the pronoun in subj