What about these relationships?

[silvery]

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!!

[Ray T]

I'm sure this has been mentioned before but, if you really want to get confused - http://videosift.com/video/I-m-my-own-grandpa-with-family-tree-diagram-Ray-Stevens

[philipsearching]

My paternal grandmother died in the 1960s, she was survived by her 2nd husband.
My father died in the 1970s, he was survived by his 2nd (bigamous) wife.
Subsequently my late father's widow married his late mother's widower.
Thank @#$% there were no children to complicate matters!

[Leanne.]

On my partners side 2 of his cousins have kids with the same women. So the kids are half sisters but also 2nd cousins. 

She was with cousin1 and had a child they were together for a short time, then about 10 years later she got with cousin2 and had a child to him. Cousin1 and cousin2's dads are brothers.

[Just Kia]

On my partners side 2 of his cousins have kids with the same women. So the kids are half sisters but also 2nd cousins. 

She was with cousin1 and had a child they were together for a short time, then about 10 years later she got with cousin2 and had a child to him. Cousin1 and cousin2's dads are brothers.

I can go a bit better here...
I have a woman who had a child with a man and less than 3 years later had a child with his brother. The children are half-siblings and 1st cousins