Google told me this: "In Russia, consensual sex between adults, including incest, is not a crime. However, under the Family Code of Russia, persons who are related lineally, siblings, half-siblings, and a stepparent and a stepchild may not marry." So, they're good in Russia, as long as they don't marry. I'm thinking, on a galactic scale, they would probably have plenty of places to express their love. At least that's how it's playing out in my fan fiction.