Around 500 sperm donors are needed each year
A 72-year-old man has agreed to become a sperm donor for his own "grandchild".
The anonymous man wishes to donate his sperm to his son and daughter-in-law who have yet been unable to conceive a child through IVF.
Any baby born using the sperm would be the grandfather's genetic child and its father's half brother.
The sperm is being screened at the London Women's Clinic, where the couple, who are in their 30s and wish to remain anonymous, are being treated.
Preliminary tests suggest the sperm is viable - it is not uncommon for men to continue to produce healthy sperm into their 70s and 80s.
Dr Kamal Ahuja, co-medical director of the clinic, said they had spent many months of discussion with independent bodies and ethics committees before reaching the decision go ahead with the treatment.
Colleague Dr Peter Bowen-Simkins said he had never come across a case like this before.
But advancements in fertility treatment meant people were now willing to consider all kinds of options.
He said: "Obviously the wife's mother-in-law also had to be included in all the conversations but she has no objections.
"Society has also changed its perceptions of what is and what is not acceptable.
"In this case, keeping the identity of the child similar to their own was a huge factor.
"The husband does not have a brother, which is why he chose his own father to assist."
No ruling necessary
A spokeswoman for the Human Fertilisation and Embryology Authority (HFEA), which regulates the fertility sector, said it did not need to approve the decision.
Donations from family members - such as sisters giving each other their eggs - are allowed under the law, she said.
Once a donor has consented to the use of his sperm for fertility treatment, he has no legal or parental rights over any children born using his sperm.
Upon reaching the age of 18, the child has the right to find out the identity of their donor father.
Dr Allan Pacey, senior lecturer at the University of Sheffield and Secretary of the British Fertility Society, said the ethics did not bother him, but safety concerns did.
"At the genetic level, sperm from older men is not as good as sperm from someone in their 25s.
"There is growing data to show sperm from older men increases the risk of miscarriage and the chances of the child having disease, as well as reducing the chances of IVF working.
"Ideally, from a best practice point of view, donors should not be older than 40."