Yup, you pronounce a plural or possessive of a word that ends in S with the es or ‘s like Travises.

However, you don’t usually pronounce an ‘s after a plural. A single Travis that owns something would be Travises. If you are referring to a family with the surname Travis, as a group, it’s the Travises. However, if the Travises own something, it will be the Travises property, not the Traviseses property.

Whether or not you write the possessive plural as Travises’ or not seems to be a matter of debate. I do. Some rules dictate that you would write the singular possessive as Travis’ and say it Travises, others would have it written as Travis’s