Moetu was driving the towing vehicle, a Mitsubishi four-by four, and when he reached the passing lanes at Waiotu decided to overtake another southbound vehicle towing a boat.
Police say Moetu and the towed vehicle were travelling about 90km/h to 100km/h when he attempted the manoeuvre. Moetu had failed to see another vehicle that had started to overtake them.
Tamara Birchall was driving north with her new fiancee Isaac Peters and her grandmother Kirihimete Paniora - a day after they had celebrated her graduation from university as a doctor.
Ms Birchall veered to miss an oncoming vehicle that had taken evasive action to avoid hitting Moetu and the towed vehicle.
Then Moetu's vehicle rolled across the road towards her and she was forced to swerve again. Her car was then struck by another southbound vehicle, killing her two passengers.
Ms Birchall, 27, who had to learn to walk again and still suffers chronic pain, had her victim impact statement read to the court by her father.
"Losing these two people I feel like I have lost part of my heart and soul. Even though I walked away it is torture to live with what happened.
"A time that should have been a time of celebration will always be remembered as a time of great sadness."
Despite the two men's careless actions she said she and the whanau forgave them.
Shona McMullien, the eldest daughter of Mrs Paniora, said mother's day was always a time to pay tribute to mums.
"Now, to me, it will always be the day my mum was killed. We were to celebrate her 70th birthday within a month of her being killed," she said.
"Because of your ludicrous decision this crash has ruined our lives."
During the sentencing Moetu and Mark stepped from the dock into the court and faced the family, saying they were sorry for what they had done.
Judge Greg Davis, who addressed the family in Te Reo during sentencing, said in his closing remarks that nothing the court could do or say would be a measure of the loss the whanau had suffered.
Moetu was sentenced to 18 months' jail, was disqualified from driving for three years and was not granted leave to apply for home detention. Fines of $3305 were also written off. Mark will spend nine months on home detention as his punishment and is disqualified from driving for two years.