I feel like it sort of depends on who has the ring. Grandfather's ring to Grandson. Grandmother's ring ot Granddaughter. That's how we've been passing down my great Grandmother's silverware. If I don't have a daughter, and my sister does, her daughter will get it. If she doesn't, then my granddaughter (if I have one, 30 years from now) will get it, or, my sister's granddaughter, and so forth.

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Alice came to a fork in the road. "Which road do I take?" she asked.
"Where do you want to go?" responded the Cheshire cat.
"I don't know," Alice answered.
"Then," said the cat, "it doesn't matter."
~Lewis Carroll, Alice in Wonderland

My grandmother died last year and currently my dad has her rings but from what I have heard I might be getting them because I am the oldest and honestly most responsible even though I do have 3 other female cousins. I have sons so if I do I most likely would leave to a granddaughter if I ever have one. My other grandma who is still living wanted me to have her wedding ring and gave to me years ago (my grandfather has been gone for many many years) she rather me have it then it sit in a jewelry box. I do wear it often!

We've always passed them on to daughters. My grandmother had two daughter and one got her ring, and the other got my great grandmother's ring. As the only daughter, I will get my mother's ring and my grandmother's ring. My daughters will get those, along with my ring. Future generations are going to need more fingers!

Its passed to the daughters or granddaughters.
My gran when each granddaughter was born bought diamond earings for that girl that will go to her when my gran passes away. I "borrowed mine" for my wedding.
All my mom jewelry has been earmarked for me.

There is an assumption in the question the son would give it to his wife to wear...maybe if the son was really close to the grandparent, he would just want it for sentimental reasons...to keep but cherish and remember. It should be left for whomever would appreciate it most...not age or sex. But "shoulds" don't always happen. I have a son and daughters...

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I just wanna live while I'm alive...

I totally agree with this. If it were me I would give it to the family member that it held the most sentimental value for.

My sisters would prefer to inherit items of monatary value but I personally would rather my grandmothers photo albums and handmade quilts.