@the_arv thank you for your work and the great plugin! I just wanted to start a new topic of this subject because I have the same problem as @jori.
Let us assume that there is Grandfather. He is father of two sons: Father A and Father B. Father A has two children: Son A and Daughter A. Also, Father B has two children: Son B and Daughter B. We can add Wife of Son B and Husband of Daughter A – the tree looks ok: https://imageshack.us/a/img696/7154/treewithoutrelationok.jpg
After Son A marry his cousin Daughter B the tree becomes messed up.
https://imageshack.us/a/img197/9632/treewithrelationwrong.jpg
This is the real situation in our family (they were married at the age of 70). Such a marrage of distant cousins may occur also in a couple of generations later. In my opinion in such a case the plugin might draw each person twice in two different branches of the tree. In the example above – the branch of Father A should have shown Daughter B beside Son A, and the branch of Father B should have shown Son A beside Daughter B. Maybe it is possible to show it other way. I hope the next version of the plugin will handle such a relation in a family ??