The plural for Mrs. Gonzales is the two Mrs. Gonzaleses; the plural possessive is the two Mrs. Gonzaleses' and the singular is same thing.
Plural: Mrs. Gonzaleses
The plural form of a word that ends in /s/ is to add /es/. Other examples are buses, glasses, and lenses.
Singular Possessive: Mrs. Gonzales's
When a proper noun ending in /s/ shows possession, an apostrophe /s/ is added. This is important to know that Mrs. Gonzales is a proper noun. This changes if it is not a proper noun.
Plural Possessive: Mrs. Gonzaleses'
The plural possessive form just adds an apostrophe when the plural form ends in /s/.
