The correct phrase is "The Thomases' house." When referring to the house owned by the Thomas family, you use the plural possessive form, as "Thomases" indicates more than one person with the last name Thomas. Therefore, the possessive is formed by adding an apostrophe after the "s."
Susan Thomases was born in 1944.
Chantal Thomass was born on September 4, 1947.
Michel Thomass was born on August 21, 1912, in Moscow.
Hollis Thomases has written: 'Twitter Marketing' -- subject(s): Business, Nonfiction, OverDrive
Eugen Thomass was born on December 24, 1927, in Munich, Germany.
Rosalie Thomass was born on August 14, 1987, in Munich, Germany.
Eugen Thomass died on January 21, 2009, in Winterthur, Zurich, Switzerland.
The plural form of the proper noun Thomas is Thomases.The plural possessive form is Thomases'.Example: The Thomases' children are twin boys named Jack and Jim.
composers
Goumon (i don't think it is spelled right)
There are two accepted forms for possessive singularnouns that end with an s:Add an apostrophe (') after the existing s at the end of the word:Thomas'Add an apostrophe s ('s) after the existing s at the end of the word: Thomas'sExamples:The meeting is being held in Mr. Thomas' office.The meeting is being held in Mr. Thomas's office.The plural form of the noun Thomas is Thomases.The plural possessive form is Thomases'.Example: The Thomases' house is number fourteen.
The Thomases is the plural form of the proper noun Thomas.Adding an apostrophe (Thomas's and Thomas') forms the singular possessive noun. Both forms are the accepted possessive form.Examples:The Thomases have a beautiful garden. (plural)Dr. Thomas' office is on the second floor. (singular possessive)Dr. Thomas's office is on the second floor. (singular possessive)The Thomases' garden is beautiful. (plural possessive)