In my English composition, I wrote the phrase "... my sister and I's favorite CD ..." According to my word processor's spell check there should not be an 's after I.

Can 's be used after I? If not how would I show possession in the above phrase?

Use "my" to show possession. Note the apostrophe "s" after "sister."

My sister's and my favorite . . .

Okay. Thank you!

You're welcome.

In English, the possessive form of the pronoun "I" does not use the 's construction. Instead, to show possession after the pronoun "I," you should use the form "my sister and my favorite CD."

To understand the reason behind this grammar rule, let's break it down. The possessive form is used to indicate ownership or belonging. In standard English, the apostrophe 's is used to indicate possession after most singular nouns and plural nouns that do not end in -s. However, for pronouns like "I," "you," "he," "she," "we," and "they," the possessive form does not use the apostrophe 's. Instead, the possessive pronoun itself indicates ownership, and you only need to add the possessive determiner "my" before the noun "sister" to indicate that both your sister and you own the CD.

So, to correctly show possession in your phrase, you should write: "... my sister and my favorite CD..."