Is there any way to tell Siri who my wife is?

When editing your own contact, scroll down to "add a related name" (I don't know the correct translation in English), tap on it, and choose your wife's contact name.

Regards

Giulio

Perhaps it's related to the fact I do use iCloud to house my contacts.

When I add a new contact, I can scroll down and see:

Spouse is one of the offerings under "Add Related Name."

Tom Wolsky wrote:

Add Related Name.

Unfortunately that destroyed my entry.

Might you be using multiple places to house your entries? Might there have been some confusion as to which place your entry had been housed, and this related name pointing to the incomplete entry?

In my own personal setup, I keep all contacts information in iCloud and nowhere else.

I can ask "Hey Siri, how old is my wife?" and receive the correct answer.

My wife is identified as my "Spouse" in contacts. Her date of birth ("Birthday") is listed in Contacts as well.

That's fascinating. ("Siri generated ..."). I've never experienced this.

If you check Settings > Accounts & Passwords, do you have only one account that shows "Contacts" there?

Tom Wolsky wrote:

Not sure the discoverability of Add Related Name is meaningful. Sounds like it's a place to enter a nickname.

Not to me ... here's why.

When I click the circled "i" to the right of the field, I am given the choice of all my contacts' names! So their data is linked to my choice.