I beg to differ. It is exactly what causes investigations for copyright infringement and for academic or creative plagiarism.
True.
Even National Comics (Superman) won its case against Fawcett (Captain Marvel) when their characters were (arguably) dissimilar; one was an alien from a dead planet, the other a boy who gained powers based on mythological gods. Not exactly twins, but enough for National to ultimately win its case.
Unfortunately, we live in a society where some (calling themselves "artists") are all too eager to swipe from the creative labors of others.
In the robot examples in this thread, one can see a design influence from The Black Hole's VINCENT and The Force Awakens' BB-8, and honestly, the Star Wars films have a long trail of sticky-fingered "influences" from endless sources across the media landscape.