Possessives Last name

[nissanmaaaan]

I'm a bit confused as to which possessive form i should use for: Valdes should i write: Valdes' or write: Valdes's I have used Valdes's in the past. Is Valdes singular or plural and do you think it sound akward as valdes's Thanks.

[2006]

Valdes is singular, and you can write/say Mr. Valdes' house or Mr. Valdes's house.
For the plural (the Valdes family's house) write/say The Valdeses' house.

Valdes's and Valdeses' have the same pronunciation.

[Horsa]

Despite the 's' ending it is not plural. As to how to form the possessive, both of your examples are acceptable so, it's a matter of personal preference. For myself, I would finish on the apostrophe and not add the possessive 's'. The only thing I would say is that it is probably better to use just one of the variations in any piece of writing rather than mix them.