I HAVE to admit that I'm baffled when I Hear English usage that's gone quite awry. I CANNOT stop thinking that things are amiss When I hear English that's spoken like this:
"Tina and I's corporation is strong." How can the speaker not see that that's wrong? "Me and Tina's" before "corporation" Likewise should bring about mortification.
"My" is possessive for "I," we should note. In grade school we all should have learned that by rote. And since the word "my" cannot stand alone, It must precede something that we have or own.
"Tina's and MY corporationβ¦" Now THAT Is hitting a homer when you are at bat! "Tina's and myβ¦" placed in front of whatever Does NOT make you sound high-and-mighty or clever,
It's merely the way to express what you mean With no trepidation of sounding thirteen. Of course, if you want, you can always say "I's," But frankly that's something I wouldn't advise.