I think that in most of Northern England, it's used for your family of one or two degrees (usually children, siblings, cousins, aunts, uncles, parents and grandparents), but it's can also be used to include people who aren't necessarily a blood relative in the family. I remember a friend at school coming in very excited one day, because her boyfriend's mum had referred to her as "our Kelly", which meant that she was being accepted as a semi-permanent fixture. Similarly, if you had a family where Daughter A's husband is "our Jack" or similar, but Daughter B's husband is only "Michael", that's giving you a fair idea of how Jack and Michael are viewed respectively.
We were also trying to work out whether you can use it vocatively: as in, can you address someone directly as "our Steve" or whatever. I reckon you can, but I'm not sure. You can use "our kid" vocatively (example!) and to anyone, and this suggests that you can use "our Mam" vocatively, but I can't work out if that's only certain parts of the North or everywhere.
My friend thinks you can't use it vocatively in Scotland, and also that you can't use it to include non-blood relatives: it is just "oor Stuart", "oor Mam", etc. for your parents, siblings and other close blood relatives.
So I'm just interested in any other comments about how it's used in Northern England or Scotland, and whether there are more regional variations or other dialects where it's used. Also, I know there are enormous numbers of ways of marking kinship in languages: do any other languages or dialects have the facility of optionally being able to include people in the family - to mark eg. that one son-in-law is part of the family, but the other one isn't really? I would also LOVE to know how it's used by Northern England bi- or multi-lingual families, and whether there's any kind of cross-fertilisation between the kin markers in Urdu or Punjabi and the "our" thing.