Amazon Grandfathered (or is it Grand Fathered") Prime Account Sharing -- possible to change/add ermail address of sharee?

Hi All,

I suspect this has been discussed to death but I am coming up empty after 30 minutes of searching

My Google search capabilities seem to be sucking as I age... I am trying to find out if there is still some way to add someone to a Grandfathered Amazon Prime account..

Current Situation: Mother shared her Amazon prime benefits with me prior to 2015

I have always been able to get free shipping with my account since sharing and she never joined the 'household program'. Don't need the streaming and other stuff..

Under my 'shared account' I created/shared a Teen account that never worked right for the free shipping, Amazon indicated that needed to be done under my mom's account to work right so I gave up

Teen is now an adult

I recall the original plan allowed for two (2) shares but I can't find where I would change that on mom's account

I see I can under my 'shared' account add someone to my household (and I think I did this a while ago and would remove the 'shared account' and try to add my 18 year old but don't want to to mess anything up. If i recall the shared account had problems but that may have been on our end..too long to remember

Appreciate any advice on this (I'm tempted to call/email Amazon) but not too optimistic that they will let me add my now 18 year olds email address to mom's account to share..

If I retreat and make it all under the new program, is it right I just need to make sure my mom has default card selected, then on my 'shared account' my own default and the orders stay separate as long as no one messes with the payment settings...