There was a show on tv over the weekend called side show freaks that talked about real side show freaks and what the real medical reason was for their condition.
There was one lady that had a "parasitic twin" which means only part of her twin developed in utero and when she was born , she was born with parts of that twin attached to her. In this one lady's case she was born with her twin's lower half, four legs, two sets of female parts, all functioning, etc, above the waist she was one person.
She married a doctor and had five children, three born in one uterus and two born in the other.
Can you imagine having double periods? I wonder if her husband kept himself busy away from home during her pms days.