Growing up on my dads side, it was nanny and grandad, great nan (sometimes oldnan don't know why)
My grandad since being a great grandad has been known as gramps to his great grandchildren. my aunty (by blood) and uncle (married) but some people would say "my aunty and her husband"
Seems weird to me...
My mums mum and stepdad were nan and pops. Her dad and step mum was grandpa and granny.
I guess this was to somehow stop confusion ect.