An Illawarra man who fathered multiple children with his biological daughter as the result of sexual abuse spanning more than a decade in the 2000s has been sentenced to 16 years jail.

The man, who cannot be named for legal reasons, pleaded guilty to persistent child sexual abuse charges in Wollongong District Court on Thursday, as well as offences relating to the sexual assault of two siblings stemming back to the 1980s.

The man's psychologist described him as "highly sexualised", saying he used sex to cope with problems in his life, beginning with the abuse of his much younger siblings, who were aged 6 and 10 at the time.

One of the siblings told the court in a victim impact statement that they had lived with the mental pain of their brother's actions for more than a quarter of a century and had been in counselling for many years as a result.

"My capacity to trust has been taken from me," the sibling wrote.