When adding possessive-S/apostrophe to a list, the rule is only the last person has the apostrophe if the item is shared, or everyone has one if they have the items each, e.g.

John and Mary's houses = the houses that belong jointly to John and Mary.

John's and Mary's houses = the houses that belong to John and Mary as individuals, at least one each.

However, I am curious if the rules are slightly different when possessive pronouns are used for a single item.

You and Mary's house OR your and Mary's house?

I'm even more unclear when the first person is involved.

Mary and my house OR Mary's and my house?

Finally, when there are at least three people, including the first person, does the last named person have the possessive-S/apostrophe, or all/none of them?


John, Mary and my house
John, Mary's and my house
John's, Mary's and my house


I'd be very grateful to anyone able to clarify this, ideally with a some form of reference, as I can't find it anywhere.



There have been several suggestions to use "our", yet if the text refers to a group of people, all of whom own co-own houses with some others within the group*, then the above style wording would be necessary, so my question stands.

* eg I own a house with John and Mary, I co-own another with Peter and yet another with Philip and Sarah.


Question: Lorentz Invariance of Maxwell Equations
Answer: Another way to see it is when deriving the EM wave equation from Maxwell equations. The  Lorentz Invariance means that the amplitude should be symmetric under translations of space and time and rotations. In the wave eq. you have only 2nd derivatives (time and space), hence symmetry under Lorentz is preserved.