What are the ethical difficulties facing those who have to decide whether to operate in the case of conjoined twins?
Mohammed and Ahmed Ibrahim - too young to make a decision
The parents of 10-year-old Indian twins, Farah and Saba, have now been told that it is feasible to attempt an operation to separate their daughters.
Now they have to weigh up the risks before deciding to go ahead.
The family and doctors of Egyptian conjoined twins Ahmed and Mohammed Ibrahim faced a terrible dilemma when deciding whether to go ahead with the operation.
The twins were two at the time of the operation, July 2003.
The adults involved knew that such an operation would put the boys at considerable risk of either one or both dying or becoming brain damaged.
However, they also knew that if the boys were not separated their condition would only deteriorate.
The decision to separate Ahmed and Mohamed was very different to that facing other conjoined twins - such as Iranian sisters Ladan and Laleh Bijani, who died during separation surgery in July.
The two cases cover some of the human rights, ethical and medical considerations facing parents and doctors in such situations.
Since Ahmed and Mohammed were only two they were clearly not able to make an informed decision about whether to choose a life apart.
One thing was for sure, their health was expected to deteriorate as they got older if they had remained conjoined.
By contrast, Ladan and Laleh Bijani were 29.
Although they were healthy adults, they accepted the risk of death in their quest to lead separate lives.
Religious questions can also come into play.
In 2000, the Roman Catholic parents of Gracie and Rosie Attard went to Britain from Malta for the girls' birth, but refused to give permission for their daughters to be separated.
The Bijani twins were able to have a say on surgery
A High Court decision allowed doctors to proceed with the separation, which led to Rosie's death.
Michaelangelo and Rina Attard argued at the time it was wrong for the courts to "play God".
After the operation they said they were relieved the judges stopped them from letting nature take its course, condemning both girls to death.
"The decision was taken out of our hands in the end but we are happy that the decision to separate was taken by the judges," said Mr Attard to a newspaper after the operation.
Doctors who cared for the Bijani sisters say there can be no routine guidelines for conjoined twins; every case is different.
In the latest case, the Indian girls are 10-years-old. Old enough to voice their opinions and say what they want, but not old enough, many would argue, to be able to fully assess the risks they face.
And so the doctors await the parents' decision.