Whether you're the older sibling, middle child, or youngest, there's nothing wrong with a bit of sibling rivalry. Growing up, our siblings can be our best friends, our worst enemies, and sometimes, both at once. If you're lucky, you'll grow out of this phase of friendly competition when you reach adulthood, though chances are you'll never be rid of it completely. 

Of course, any rivalry may be exacerbated by proximity, as in the case of the Siodmak siblings. Robert and Curt Siodmak both grew up to be famed directors. While Robert became known for films like The Killers (1946) and Flesh and the Woman (1954), Curt directed movies like The Wolf Man (1941) and The Invisible Man Returns (1940).

The two briefly worked on the same project, Son of Dracula. The 1943 film was directed by Robert Siodmak from an original story by Curt Siodmak. However, Curt left the project after his brother signed on as director.

According to Universal Horrors: The Studio's Classic Films 1931-1946, written by Tom Weaver, this departure wasn't just happenstance. The book claims that Robert actually had his brother removed from the project. During an interview, Curt Siodmak discussed his relationship with his brother, stating that the competitive nature between the two had existed for years, even while the two still lived in Germany.

"We had a sibling rivalry," said Curt Siodmak. When we were in Germany, Robert had a magazine, and when I wrote for it, I had to change my name. He only wanted one Siodmak around. This lasted 71 years until he died."