<< Back to glossary index


Relatives that share 12.5% of their DNA, for example first cousins.

Use in clinical context

Individuals who are related share DNA, as it is passed on to each subsequent generation at fertilisation. The percentage of DNA that individuals in a family share varies depending on the degree of relatedness – closer relatives share more DNA than more distant relatives.

Due to recombination, third degree relatives may share very little of their DNA, or a large amount, but on average they share 12.5% of their DNA.

Third degree relatives in a genetic family history are identified as those individuals with two other family members between them, for example first cousins.

Last updated on 31st May, 2019