Sorry for the delay in coming back to you!!
So, my grandfather was Owen Cosker who I died last year. His father was James Cosker, the youngest son of Owen and Mary Cosker, who lived in Wigtown. James had an elder brother, also called James, who died in a drowning accident in Wigtown, whilst his mother was pregnant with James II and there is a plaque in the local church commemorating him.
James had other brothers and sisters, Agnes; Mary; Susan; Lizzie; Arthur and Harry. They were the children of Owen and Mary (James’ brothers and sisters.
James married Annie and had six children Angie; Owen; George; Jim; Arthur and Marie. Owen was my grandfather.
I should connect you with my Aunt, Patricia Cosker who did some research into the family.
My mum and aunt are both Coskers by birth, both have since married.