Healthy mice have been born to two mothers and no father, researchers have said.
The bimaternal mouse pups, produced through complex gene editing, went on to have normal offspring of their own, according to a study published in journal Cell Stem Cell.
Mice were also born from two fathers and no mother but only survived for a couple of days.
The study was carried out by researchers at the Chinese Academy of Sciences.
Some reptiles, amphibians and fish can reproduce with one parent of the same sex.
But it is extremely difficult for mammals to, even with the help of the most advanced technology.
To produce healthy bimaternal mice, the researchers used haploid embryonic stem cells from one of the parents, containing half the number of normal chromosomes and DNA.
They then used gene deleting techniques and injected the cells into the eggs from another female mouse.
They produced 29 live mice from 210 embryos, with the animals living to adulthood and having offspring of their own.
The researchers also produced 12 full-term mice with two genetic fathers, using a similar but more complicated procedure.
These were transferred, along with placental material, into surrogate mothers.
The bipaternal mice pups only survived for 48 hours after birth.
Co-senior author Qi Zhou said: “This research shows us what’s possible.
“We saw that the defects in bimaternal mice can be eliminated and that bipaternal reproduction barriers in mammals can also be crossed through imprinting modification.”
But experts warned that translation of the technique to humans was extremely unlikely.
Dr Dusko Ilic, from King’s College London Faculty of Life Sciences and Medicine, said: “The study is shedding light on various aspects of mammalian reproduction and development and it is opening new avenues for future research.
“To consider exploring similar technology for human application in the near future is implausible.
“The risks of severe abnormalities is too high, and it would take years of research in various animal models to fully understand how this could be done safely.”
Dr Christophe Galichet, from The Francis Crick Institute, said: “The authors have made an extremely important step forward in understanding why mammals can only reproduce sexually.
“In mammals, some genetic information must be given by mum or dad chromosome in order to generate an offspring.
“While human haploid embryonic stem cells, cells in which only half of the chromosome are present, have been generated, it is unthinkable to generate a human baby that way.”