Has to be in the same household (address) is what I have been told for spouses/domestic partners. They don't have to be added to the contract.

Bringing any kind of documentation might help you as an agent can override most anything.

"Hertz’s website says it exempts unmarried partners who permanently reside together at the same address and who are members of its loyalty program, and Avis’s website says it exempts life partners. But representatives at locations for those companies said that only spouses could be added as additional drivers for free. Enterprise said it verified spouses and domestic partners by matching the addresses on the driver’s licenses."

https://www.nytimes.com/2022/02/24/u...ental-law.html