Unprovable, but it's almost certain SOMEBODY has.
While the Soviets DID launch Valentina Tereshkova, the first woman in space, in 1963, TWENTY-TWO YEARS before the U.S. had a woman fly, she did however fly solo. But in 1982, Soviet cosmonaut Svetlana Savitskaya was part of the first mixed-gender crew, on...
Best answer: Unprovable, but it's almost certain SOMEBODY has.
While the Soviets DID launch Valentina Tereshkova, the first woman in space, in 1963, TWENTY-TWO YEARS before the U.S. had a woman fly, she did however fly solo. But in 1982, Soviet cosmonaut Svetlana Savitskaya was part of the first mixed-gender crew, on the world's fourth space station (the first three were also Soviet). This was a year before the first American woman ever left the atmosphere.
There have been lots of mixed crews since then, Russian, American, mixtures of both, and other nationalities. Plus, several space travelers, male and female both, have turned out to be gay. Over 530 people have been offplanet, 55-plus of them women (according to my memory, but both of those numbers are certainly higher now), including one female commercial passenger (a naturalized American from Iran, named Anousheh Ansari).
While press agents for both NASA and the Russian Space Agency have refused to comment when asked about it, it's damned near certain that SOME kind of sex in microgravity has happened already.
Spacers are PEOPLE. When's the last time you heard of over 500 people going ANYWHERE, and there was no sex?
There have also been a number of people born who are "space babies" -- born after both of their parents were in space. The first was Dr. Elena Nikolayev, born in 1964, whose mother, Valentina Tereshkova, was the first woman in space. Her father was pioneering Soviet cosmonaut Andriyan Nikolayev.
Soviet, and later Russian, scientists have given Doc Elena a THOROUGH going-over, both short-term examinations and long-term observation, and there appears to be nothing special about her (other than the fact that she's real smart, a celebrated physician, and kinda hot. But that has to do with having smart and goodlooking parents, not with them having been offplanet). And if I recall correctly, she's had kids herself, and THEY were ok, too. (Imagine the schoolyard boasting! "Oh, so your grandma can bake a good cake? So what? MY grandma was the first woman in space!")
Spacers tend to get along well. They understand each other, and they share the amazing experience of having gone up and out, to where the blue turns to black. There have now been quite a few "couples" who've both been up, both just dating couples, AND long-term. Some of them went up together.
Puritanism of space agencies notwithstanding, there's no logical reason to assume all of those relationships were only consumated on Earth.