I came across some blood relations / intra family marriages like first cousin marriages in some of my family history books that I have. They are all documented as text in a family history book, not as a pedigree. I tried MyHeritage.com to draw such a tree, but no luck. I don't think I can loop back a child node to an ancestor and create a marriage relation, but has to create another duplicate tree.

Reading about Albert Einstein's family history, I came across such a diagram. Is this the right way to show a family tree which has first cousin marriages or is there a better way? Is there a software or website where I can do something like this?