Should you write about "Ryan and Katie's cake" or "Ryan's and Katie's cake"? It's a tricky compound possession question.
A listener named Katie wrote in with this question:
How do you show possession to more than one noun?
For example, would you say, “Tom and Jerry’s TV show” and “Ryan and my anniversary”? The latter looks so odd that I end up avoiding it entirely and going with a longer and less efficient, “Ryan and I are celebrating our anniversary on…”
Thanks for the question, Katie! What you’re asking about is called “compound possession” or “joint possession.”
I’ll start with the first part of your question.
1. With Nouns, How You Write a Compound Possessive Depends on Whether Things Are Shared
If you're trying to write about possession and you have two subjects that are nouns, you have to decide if the two people possess something together or separately.
If the two people have the thing together, they can share the apostrophe-S. If they don’t share the thing, then they can’t share the apostrophe-S either. They each need their own.
So, to use your example, if you’re talking about Tom and Jerry’s TV show, they’re the main characters on the same cartoon about a cat and mouse—essentially they share the show—so they can share the marker of possession, and you need only one apostrophe-S at the end: It’s Tom and Jerry’s TV show.
If they are on the same show, it's 'Tom and Jerry’s show.'
But let’s say you’re talking about two characters who each have their own TV show. Imagine that Tom hosts a show about famous cats for Animal Planet, and Jerry hosts a spin-off of “MTV Cribs” that is all about tricked out mouse habitats. Now imagine that both those shows got canceled. You’d need to write that “Tom’s and Jerry’s shows were canceled,” putting an apostrophe-S after both “Tom” and “Jerry.” Because Tom and Jerry each have their own separate show, they each also need their own apostrophe-S in that sentence.
If they are on different shows, it's 'Tom’s and Jerry’s shows.'
The same is true if you have more than two people in your sentence: If they all share the same thing, you put one apostrophe-S on the final name in the list. If you want to include the bulldog Spike from the cartoon show, you can call it “Tom, Jerry, and Spike’s show.”
If they all have different things, they each need their own apostrophe-S, although that can get cumbersome. If Spike had a show on HGTV about doghouses, and it got canceled too, you’d have to write that “Tom’s, Jerry’s, and Spike’s shows all got canceled,” giving each of them their own apostrophe-S. At that point though, you might want to rewrite it to something like “Tom, Jerry, and Spike each had a TV show, but they all just got canceled.”
Here’s another example. Let’s think about something a little more abstract: beliefs.
Remember: The rule is if multiple people share something, you use one apostrophe-S. So if Steve and Amy have the same religious beliefs, it is correct to write about “Steve and Amy's beliefs” with only one apostrophe-S after the last noun.
On the other hand, if Steve and Amy have different beliefs, then you’d write about “Steve's and Amy's beliefs,” giving each of them their own apostrophe-S.
2. When Mixing Nouns and Pronouns, They Each Need Their Own Possessive Form
Now let’s get to the second part of Katie’s question. What about “Ryan and my anniversary”?
Even though you share the anniversary, now that you’re combining nouns and pronouns, one possessive can’t do the work for the whole subject. You have to make them both possessive in their own way. So the noun needs to be possessive ("Ryan’s"), and you use the possessive pronoun (“my”). “Ryan’s and my anniversary.”
A side point is that you always put yourself last in a subject like this, so it’s “Ryan’s and my anniversary,” not “My and Ryan’s anniversary.” I think of it more as a matter of politeness than strict grammar, as if Katie is holding the door open for Ryan and letting him walk through first.
Although sentences like this are grammatically correct, they can sound odd to a lot of people, and Katie had the right idea. It’s usually better to write them a different way. For example, instead of "Steve’s and our beliefs guide our actions,” try something like “We and Steve let our beliefs guide our actions.” But since it’s grammatically correct, it’s up you what sounds right and what sounds weird.
3. ‘I’s’ Is Not the Possessive Form of ‘I’
Finally, this topic reminded me of something I’ve been noticing for a while: “I’s,” as in I-apostrophe-S. And I’m not alone. A few months ago, a woman named Allegra tagged me on Twitter:
Because I mentioned it in my IG story this weekend and people still didn't understand: "I's" is not ever correct. "Her and I's relationship" is NOT a thing. "Our relationship" or "my relationship with her" are both correct. Where did this come from? @GrammarGirl — Allegra Swanson (@ayoungvoice) August 6, 2019
I’m not sure where it came from except that people are confused about compound possessives and pronouns, but if you do a Twitter search for "and I's," (which brings up things like “Ryan and I’s relationship”), you get a surprising number of hits. Surprising.
So I will repeat Allegra’s advice: “I’s” is not the possessive form of “I.” It is not “Ryan and I’s relationship.” “Our relationship” works, but if you want to keep the noun and pronoun form, the word you want is “my.” It is “Ryan’s and my relationship,” with both words in their possessive form: “Ryan’s” with an apostrophe-S as the possessive form of the noun “Ryan,” and “my,” as the possessive form of the pronoun “I.”
3 Rules to Help You Form Compound Possessives
To sum up, we learned three things about compound possession: First, if you’re just working with nouns, if the people share something, they can share the possessive form, and you put the apostrophe-S on the last name or last item in the list. If they don’t share the thing, then everyone needs their own apostrophe-S.
Second, if you’re mixing nouns and pronouns, both need to be in the possessive form whether things are shared or not.
Third, the proper possessive form of “I” is “my,” not “I’s.” So Katie is correct to write about “Ryan’s and my anniversary,” not “Ryan and I’s anniversary.” And by the way, happy anniversary!
Image courtesy of Shutterstock.
Mignon Fogarty is Grammar Girl and the founder of Quick and Dirty Tips. Check out her New York Times bestseller, "Grammar Girl’s Quick and Dirty Tips for Better Writing."