Joint Ownership 

Let’s talk a bit about joint possession and the proper way to express this. Possession can get a bit tricky, and writers often don’t stop to think about the nuances. Take a look at this sentence:

• We always go to my uncle and aunt’s house for the holidays.

Unless your uncle and aunt have separate homes, the sign of possession—the apostrophe—is placed with the second noun. The pair is treated as a unit; that’s  what joint ownership is, after all.

Things get a little trickier when you replace one of the nouns with a pronoun. Which is correct?

• We’re going to him (referring to your uncle) and my aunt’s house
• We’re going to his and my aunt’s house

Remember your grammar teacher talking about possessive adjectives? These are pronouns that do not replace a noun but precede a noun and show possession. Very convenient in situations like these. His, hers, ours theirs, my, your, and its are all possessive pronouns. No apostrophe required.

So in our example, choose the sentence with the possessive pronoun his, replacing uncle.

Should you reverse the order, both the apostrophe and the possessive pronoun are necessary to show joint possession.

• We’re going to Aunt Sylvia’s and his house.

Beware of replacing both nouns with pronouns, especially if one is a personal pronoun. It’s fine to say “I’ll give you his-and-her towels,” but avoid constructions such as these:

• Your and my children (our children)
• Their and our investment (their investment and ours)

And my favorite:

• My and you guys’s party is about to start.

Do I really have to point out how bad that is?