At the man's sentencing at the North Shore District Court, Judge Lawrence Hinton said "all taken together, they are very serious charges indeed".
He called the man's offending against his son "heinous" and said it started in 2009 in the family home when the boy was 11 years old.
The Herald has decided not to detail the graphic offending though the judge said it was "grossly offensive" and encompassed a "wide range of sexual activity".
In effect, the man had "groomed" his son from age 11, Judge Hinton said.
"There was particular vulnerability given your relationship. You were his father, he was your son. He was entitled, like any son, to expect more from you," he told the court.
"It was a gross breach of trust in any event by a parent against a child."
The other offending involved young boys and girls, sometimes siblings.
The man admitted rubbing the victims' shoulders, arms and thighs and gave inappropriate massages at their own homes.
In the case of one of the teenagers, the man started by rubbing different parts of her body inappropriately in 2009.
When she reached adolescence, he put his hands under her top and rubbed her breasts and groped her bottom underneath her underwear. The offending continued for five years.
The man pleaded guilty to all of the charges at the earliest opportunity. He was charged with:
• 2x unlawful sexual connection against his son
• 6x sexual conduct with a child under 12
• 15x sexual conduct with young person under 16
• 3x indecent assault
Judge Hinton said there been an obvious breach of trust and harm caused by what the man had done.
Yet his victims asked the court to recognise the man's "good qualities".
His wife and a number of the families read statements, though the details have been suppressed.
But Judge Hinton said one of the parents had been "obviously distressed" by the man's offending because he'd "effectively preyed" on her son who was particularly vulnerable as he was attempting to overcome dyslexia.
Another parent spoke of feeling betrayed, fooled and manipulated.
But the judge said the woman was gracious with her comments and sought a merciful intervention by the court for his "honourable qualities, which she thought would triumph".
The man's wife also spoke of his "good qualities" and was eloquent when describing her trauma, shock and betrayal, the judge said.
"She has been devastated by grief and seeing the suffering of the children and the indescribable violation of her precious boy."
Prosecutor Fiona Culliney said the Crown accepted the victims' wishes and man's remorse though sought a minimum non-parole period to protect the community.
Judge Hinton agreed and said the man needed to be held accountable and his conduct denounced despite "stepping up to the plate" and pleading guilty, which saved a trial.
The court needed to impose a deterrent, not just for him, but "from a public perspective that a loud and clear message is given to the community".
He accepted the man's remorse, previous good character and gave him a 5 per cent discount for those mitigating factors as well as 25 per cent for his plea.
"We must all recognise that you're a human being like the rest of us."
Judge Hinton jailed the man for 10 years and six months in total for all of the charges with a minimum non-parole period of four years and two months.
The man was also given a three strikes warning and put on the sexual offenders register.
