I doubt if there has ever been a genuine true human hermaphrodite. By my understanding, fully functional male and female reproductive systems cannot both exist in the same body at the same time, due to different hormonal balances required by each to function.
I have a rather bizarre movie in my collection, titled
Predestinaton, which is based on a short story by Robert Heinlein titled
All You Zombies. The protagonist in this story could be described, I suppose, as a serial hermaphrodite. The character is presumed to be a girl, when she is found as a baby abandoned on the doorstep of an orphanage in 1945. Her girl parts are ruined by a botched C-section in 1964, but in the process, the doctors discover complete boy parts in her as well, and begin the process of rebuilding her as a man.
Time travel is involved, which leads the story of this character in some very weird directions. The male version of this character travels back in time and meets the female version, knocks her up, and then leaves her. A few weeks after the healthy baby girl is born via the aforementioned botched C-section, a much older version of the same character kidnaps the baby and takes her back to 1945 and leaves her on the doorstep of an orphanage.
Could such a character exist? I mean, aside from the weirdness that time travel infuses into the story, could a person exist, who had both male and female reproductive parts, with one side working, and then, after one side had been destroyed, the other side could be made to work? I can think of a way that it might be possible. Sexual morphism is largely controlled by hormones, but my understanding is that the gonads, which are at the key to the distinction between male and female, and the key to the ability to function in the reproductive roles of either, are strictly genetic-based. In mammals, including humans, if a gonad has XY chromosomes, then it will develop into a testicle, and if it becomes functional, it will produce sperm cells. If it has XX chromosomes, then it will develop into an ovary, and if it becomes functional, it will produce ova, or egg cells. The various improper conditions that have extra X or Y cells will usually produce gonads that simply won't function fully; if they do produce games, then those gametes will be sperm if thee is at least one Y chromosome, and ova is there is not; but usually, these other combinations are sterile.
So, a normal, monozygotic human cannot possibly have both ovaries and testicles. The way that I can see it being possible was that if the individual was a
chimera, one person composed of what were supposed to be two different fraternal twins, one male, and one female, in which, in the course of fusing into one person, both sets of gonads were persevered. Which ever set of gonads ended up dominant in the early stages of development would get to control the hormonal balance, which would determine the sexual morphology that would develop, but the other set would still be there, inactive, and could possibly be activated if the hormonal balance was changed.