A father and daughter convicted of incest in Dunedin have been sentenced before.

The pair were found guilty yesterday for a relationship they started six years ago, when the father was 29 years old and the daughter 16.

After a conviction in 2012, they were ordered to stay away from each other.

However, an investigation a year later brought the latest offending to light.

Sex Therapy New Zealand's Mary Hodson told Mike Hosking genetic sexual attraction has been studied by researchers and psychologists around the globe.

"It seems to be associated with a deep sense of longing for a relationship with the parent or the child, when the relationship can't happen."