One woman said she wished her family had done something all those years ago instead of "stupidly" believing the offending would end with that meeting.
Their uncle, possibly about 25 years old at the time, might have got the help he needed and other young relatives might have been spared his offending, she said.
The women were giving evidence in a jury trial for the man, which began last Thursday in Whangārei District Court and continues this week.
The accused, now is in his late 50s, cannot be named due to suppression that applies automatically to the complainants.
He faces 30 charges arising from complaints by seven of his female relatives.
The charges span 1979 to 2018 and reflect the law as it stood at various different times: 18 counts of indecencies with underaged girls; rape; six counts of sexual violation – three by rape and three by unlawful sexual connection; and five counts of sexual conduct with a child overseas – when they were both living in Australia.
Evidence from the two sisters, now aged in their early 50s, followed that of a similarly-aged cousin who alleged the man raped her at a school swimming pool when she was about 11.
The two sisters' each complained of single incidents in which the man allegedly indecently assaulted them during the early 1980s.
Each said it happened in situations where they were sleeping on mattresses on the ground, surrounded by other cousins.
One said she was about 11 when the man – then 17 or 18 - touched her genitals in a lounge room of her grandparents' house and near their open bedroom door.
It was dark but she knew it was him – he was the oldest and biggest in the room, the woman said.
It was painful and she tried to scream but no sound came out.
She moved to a couch, where she kept her eyes shut and quietly cried. Then she felt "big lips" on her face - also her uncle's, she said.
Frozen, she "just kept crying hoping he would go away and he did".
"After that, I can't really remember anything... I just think it was the shock of the pain and of being that age and him doing that to me.
"That was the only incident I remember but yeah, I suppose it has affected me still," she said.
She "shut it out" not telling anyone until years later when an aunt (the man's sister) approached her saying something had happened to a cousin.
The other sister said she was between 11 and 15 years old when the man - four years older than her - rubbed his body up against hers in a tent during a family camping trip.
He smelled of beer.
Knowing he would not leave her alone, she quietly said "no" then moved into a beam of light, where people would see her if they woke up.
It made her feel safe but she often got "pissed off" now realising he might then have assaulted someone else, the woman said.
She recalled this incident because it was the last one and by then she was old enough to know what he was doing was wrong.
She also recalled a first incident (for which the man would have been too young to be prosecuted. She said there were likely other times too but she had "probably blocked out" those.
Cross-examined by counsel Russell Boot the women were emphatic the offending happened, that they were not lying or under pressure by anyone to complain, and had not colluded with other complainants.
They refuted Boot's suggestion their uncle might have been younger at the time of the claimed meeting and that if he apologised, they might have misunderstood the reason for it - that he could have been apologising for behaviour as a boy under 14.
SEXUAL HARM - DO YOU NEED HELP?
If it's an emergency and you feel that you or someone else is at risk, call 111.
If you've ever experienced sexual assault or abuse and need to talk to someone contact the Safe to Talk confidential crisis helpline on:
• Text 4334 and they will respond
• Email support@safetotalk.nz
• Visit https://safetotalk.nz/contact-us/ for an online chat
Alternatively, contact your local police station.
Where to get help:
• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• Helpline: 1737