Nichols Ray ( a film director) was married to Gloria Graham and they had a son (a). One day Ray came home to find Gloria in bed with his 13 yr old son by a previous marriage. Eight years later this son, now aged 21, and Gloria got married and had two children.
So - the half brother to son (a) (also now his stepfather) was also the father of the later two children, who were also half brothers to son (a). How to enter that into a tree!!