Donor-conceived Australians are desperate to know their biological family, with many terrified at the prospect of unknowingly sleeping with a sibling.
Their fears are prompting calls for world-first legislation to enshrine the legal right to know not only your biological parents, but your siblings.
The concerns were among many shared on Friday at a public hearing as part of a NSW inquiry into fertility support and assisted reproductive treatment.
The inquiry was told about a situation in which two people in NSW married before discovering they shared a sperm donor and were genetically siblings.
Currently, each state has its own system for handling these fertility issues, including different limits on how many families a sperm donor can contribute to.
Genea Fertility chief executive Tim Yeoh called for a national donor registry and a uniform 10-family cap on contributors.