A Victorian man said he was sick and glad he was caught after filming himself sexually abusing his infant twin daughters and sharing the footage online.
The father paid $44,000 for a surrogate to carry his twins, conceived with a donor egg, then brought the babies to Australia for his own sexual gratification, prosecutors told a court.
He faces a lengthy jail term after a police raid on his family home in November 2014 uncovered 26,343 child exploitation videos and images, many documenting his abuse of his daughters and nieces.
More than 16,677 images depicted his nieces, whom he abused for four years starting when they were aged 4 and 6.
He abused his daughters weekly for eight months starting when they were just 1 month old, the Victorian County Court heard on Friday.
Crown prosecutor Krista Breckweg said material recovered from the man's computer was "disgusting".
The man, who cannot be named, has pleaded guilty to 37 charges including trafficking children, producing pornography and 20 counts of sexual penetration of his own child.
He will be only the second person to be sentenced for child trafficking in Victoria.
"I'm not upset at getting caught, I'm upset that I'm stupid and sick," the man told police following his arrest.
"I love them so much and I don't know why I did it."
Ms Breckweg said by his plea the man admitted bringing the babies into Australia for sexual services.
"The chat-log shows the conduct he fantasised about ... did actually occur," Ms Breckweg said.
The man would wait until his wife went shopping and abuse the girls on the weekend, making the footage and stills available online, the court heard.
The Crown said the man's wife of 26 years was not complicit in the offending, but has been subject to suspicion and the children were removed from her care.
"It had a devastating effect on her life," Ms Breckweg said.
Defence barrister Jarrod Williams told Judge Susan Cohen the man recognised what he did was very, very wrong.
His behaviour escalated after he first viewed child pornography in 1994, but he had exhibited unusual sexual behaviour, including stealing underpants from clothes lines when he was 18.
During the police raid he told his wife: "I'm a pedophile and I'm going to kill myself".
In a letter to the court he said there was no excuse for the suffering he had caused.
"I have destroyed and ruined innocent lives," the man wrote.
"I will never be able to forgive myself."
Ms Breckweg said when the man made the admissions to police he knew all the material on his computer was going to come out.
The man kept his head down during the plea hearing.
Judge Cohen will sentence on a date to be fixed.
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