Q: What is the rule for the plural spelling of surnames? My Thunderbird spell-checker adds an apostrophe. But the consensus on the mailing list of the Association of Professional Genealogists is that the apostrophe is not required. What are your thoughts?
A: An apostrophe is NEVER added to a straight plural. Only possessive names (both singular and plural) get apostrophes.
Here are some examples of how to treat four family names.
Surname: Brown … Jones … Smith … Lopez
Plural: Browns … Joneses … Smiths … Lopezes
Singular possessive: Brown’s … Jones’s … Smith’s … Lopez’s
Plural possessive: Browns’ … Joneses’ … Smiths’ … Lopezes’
I hope this helps! If you’d like to learn more, you might check out “Comma Sutra,” the chapter on punctuation in my grammar book Woe Is I.