Apostrophe Use in Plural Last Names

[RealityChuck]

Strunk (and White) says the singular possessive of most names is simply adding the “'s”: syllables aren’t a factor. Thus, Lucas’s car.

@Strunk and White

Form the possessive singular of nouns with 's.
Follow this rule whatever the final consonant. Thus write,
Charles’s friend
Burns’s poems
the witch’s malice
This is the usage of the United States Government Printing Office and of the Oxford University Press.

Exceptions are the possessives of ancient proper names in -es and -is, the possessive Jesus’, and such forms as for conscience’ sake, for righteousness’ sake.