"Of course no penalty that this court can impose can heal these women."
At the time of the abuse the girls were aged under 12 and between 12 and 16.
One girl was aged between 8 and 11.
Judge Barry told the court how the man, after assaulting the girls, would threaten them.
"Your first victim was your sister. This started when she was about 10; you would have been about 14.
"There were threats of violence against her if she told anyone what had happened.
"The second victim was a cousin. That indecent offending occurred from about 1969 to 1973, when you were aged 19 to your early 20s; she would have been aged about 8 to 11 ... again this offending was accompanied by threats to ensure her silence."
Judge Barry said the offending was planned and "opportunistic".
"Preying on children when the coast was clear and parents were away was compounded by threats and intimidation used to buy their silence.
"These were young and totally vulnerable children and the harm that you wrought on them is considerable."
He said the man's offending was mitigated by the fact he was "genuinely remorseful", had lived an otherwise offence-free life, had offered to pay emotional harm reparations and was a youth at the time of the offending, aged under 17 and between 19 and his early 20s. He was also given credit for an early guilty plea.
Crown prosecutor Andrea Ewing said the offending was persistent and premeditated, that the man had breached the trust of the girls and that on occasions it had happened while he was babysitting them.
Ms Ewing outlined the impact of the man's offending on the women.
"[One woman] has spoken movingly about how chaotic her life became as a result of this offending. She suffered from depression and had difficulty with personal relationships.
"She suffered from isolation, especially from her mother who was the person she most wanted to tell what was going on.
"She is suffering from flashbacks still and just feels that the damage that has been done here can't be put into words."
Defence lawyer Phillip Drummond said the man had provided a $10,000 cheque for emotional harm to the women.
Mr Drummond told the judge that the man, if sentenced to imprisonment or home detention, would lose his job of 28 years as a manual worker.
However, Judge Barry sentenced him to nine months' home detention and 150 hours of community work.
He also ordered the man to pay reparations of $5000 to each woman.