My grandmother was told that she had the same father as her older siblings. Her mother divorced her husband and married a gentleman who had been a boarder for a period of time. She was shunned by the first husband when he would see the older children. Her mother and the 2nd husband had 1 son together. They have all since passed on.
However, my mother and her cousin are still alive. The cousin is the child of the 2nd husband.
I am trying to determine which man was my grandmothers biological father.