I call my DSPs by their first names.
I am close to both sides - my Ddad & my DSdad both walked me down the aisle at my wedding.
I adore my Ddad's partner - she is great, but I don't think of her as a step 'mother' and I don't think she thinks of me as a step 'daughter' although I do think of her as family. She is a similar age to me and her relationship with my father started when I was in my late teens. They have been together for 6 years now.
Anyway, when mine & DH's DCs come along they will definitely call my DSdad 'Grandad' as well as my Ddad. They will call DSdad's parents great grandad/ma.
What should they call my Ddad's partner?
She is 25 so it would be odd if they shouted 'grandmother' after her.
What do you all do?