Great Aunts I think.

My father's mother died young, and I think these were her sisters. On the back is written Isa and Bessie, Kilmarnock. Or it could say Ira and Bessie. ScotlandsPeople shows that she had a sister Elizabeth which could be Bessie. The other sisters are listed as Helen, Jane, and Christina: I guess any or none of those could have been caled Isa/Ira.

I'm not aware of any family connection with Kilmarnock - the Stobie family moved from Edinburgh to Glasgow before my grandmother married a man from Banff. But my father and several of his siblings were born in Strathaven, and we don't know why, so maybe this hints at an explanation.