To not really want DS to call my mum's partner 'Granddad'?

[Tiddlyompompom]

I am curious as to what the expectation would be from other people, having just read a thread about Uncles not being called Uncles.

My mother wants my son to call her partner Granddad. I'd rather he didn't, as he's not my father, and I don't consider him my stepfather either - they've been together five years, but I'm 34, he's just my mothers partner and not a parent to me. He's a perfectly pleasant chap and lovely with DS but not someone I love, and I don't particularly want my son growing up thinking he's my dad.

My sister has neatly sidestepped this whole issue by her kids calling him 'Granddad Jim' not his real name and I was planning to do that too, but now my mum says she doesn't like it and wants DS to call him just Granddad.

DS won't ever meet his 'real' Granddad as he's a twat who can't be bothered as we've lost touch, and I've had two other long-term stepdads since, however DH's father is very much around and called by another Granddad-type name.

I'm not massively upset by this or anything, but I just feel that it's ok to acknowledge the difference between a blood relative Granddad, and Granddad Insert-name-here who is Granny's partner.
It is quite clearly not meant as a slight or insult, in the context of my family, but I do see how others could poss see it that way.
AIBU?

YANBU I am in a similar position my DM has been married to my SF for 8 years (they hadn't been together long before they got married) but as I am 31 and I didn't live with DM when they met I don't really know him that well my eldest dd who is now 11 obviously just calls him by his name as I certainly wouldn't have let her call him grandad when she was younger because I lived quite far away from them and I didn't know him at all. Anyway my youngest dd was born in 2010 and my DM asked me if SF could be known as "grandad" to her? Myself and Dh both said no because eldest dd calls him by name so it should be kept at that for youngest dd too, she did try and push her luck after we said no by referring to him as grandad again when she was visiting but I told her again and she hasn't done it since! For me I think if he played a part in their lives I would think about it more but he doesn't.

YANBU, my dad remarried after my mum died and he would never expect my dcs to call his wife grandma. They call her by her first name. She is a perfectly nice woman but she is not their grandma, my mum was . His wife doesn't mind either.

We're a very extended family and here's what has worked for us:

ds2 and ddil have a daughter. I'm her Nanny and ddil's mother is Grandma.

ds2's father (my ex-h) is Grandad. ddil's father (divorced from her mother) is Grandpop. My DP is Grandpa (his name). ddil's mother's dp has a nickname used only by dgd.

This system seems to avoid Fake Granddad Syndrome as well as give everyone who plays a grandfatherly role in dgd's life a special and meaningful name.

My dad remarried to someone I wasn't especially keen on. My sister's children who were 10 years older than mine called her by her first name.
Because mine were younger and didn't ever know my mother they called her Granny, which wasn't the name my mum had been known by anyway.
They were all well aware she wasn't my mum and I wouldn't really have wanted them calling her by her first name as they were so young.
I don't think it hurts to be honest. And she was a pretty reasonable granny to them on the whole (and they really missed the fact that they hadn't had one), even though she was a pain as a stepmother