Trying to update duplicated symbols

Ok here goes. This seems so simple. What’s wrong with me???

I have a button symbol in my library. I then duplicated it a few times to create some child symbols from it. Now I thought if you change the parent button that the child symbols could be updated but when I drop the menu in the library for the child symbols the update option is greyed out.

What’s going on? Please help.

Thanks
Kel

bump