Complex sentence: Jack Kubrick, whose parents and paternal grandparents were of Polish, Austrian, and Romanian origin, was a doctor, graduating from the New York Homeopathic Medical College in 1927, the same year he married Kubrick's mother, the child of Austrian immigrants.
Split into simpler sentences: Jack Kubrick, whose parents and paternal grandparents were of Polish, Austrian, and Romanian origin, was a doctor. His father studied medicine, graduating from the New York Homeopathic Medical College in 1927, the same year which he married Kubrick's mother Gertrude, the child of Austrian immigrants.