"It's probably why we had so much energy at school," is Tumanako's take on that.
Then there's their koro Tommy Bidois who's been an inspirational role model to them equally.
"He's done an amazing amount for his Ngāti Rangiwewehi community, things like building coffins for those who can't afford them, it's the high standards and principles he holds that inspires us." That comes as a joint statement.
Although born three years apart, these are siblings who are much more twin-like than your average brother and sister.
If they aren't speaking in unison, one starts a sentence, the other finishes it, their bond is super glue-tight. When Eru marries at the end of this month Tumanako's to be his best man.
But they scotch any suggestion they're a double act, each is as insistent as the other they are individuals.
"We are different enough to be individuals but similar enough to have the same aspirations." More unison speak here.
Nine days ago they were jointly awarded Bev Anaru Educational Memorial Scholarships. Tumanako's was to help finance her way through medical school which she enters this coming week, so goes bolstered by an Auckland University Bachelor of Nursing.
Eru, a newly graduated doctor, attempted to give his $5000 back to donor Pita Anaru, who established the scholarships in memory of his late wife, a staunch advocate for on-going qualifications for young Māori.
"I felt guilty getting it because I had already graduated but Uncle Pita said 'keep it and spend it on something to make you a better person for our people'. That's a challenge I appreciate and intend to fulfil - absolutely."
The Bidois duo grew up steeped in all things Māori.
Their education was kick-started at kōhanga reo in Tauranga and from the time they arrived back in their father's mana whenua (home territory) in 2001 their education was total immersion Māori at Te Kura Kaupapa Māori o Te Koutu.
"We feel we were so lucky to have this when our koro was beaten at school for speaking Māori."
Both went on to be head prefects and dux of their respective years, they've also been recognised as Rotorua Young Achievers.
They agree it was their commitment to their studies that earned them the "nerd" school yard teasing they received.
Although Spanish was a compulsory subject at the kura other lessons weren't in English until their final year. When classes such as science became more complex, they were studied through Te Ahu o Te Kura Pounamu, the New Zealand Correspondence School.
Tumanako shone at maths. "I credit our parents with that, they had this big poster on the wall with all the times tables and insisted we memorised it from when we were very young, that grounding really helped me."
The Bidois' may have been "nerds" academically but both were also into sport. For Eru that was football and volleyball, however he concedes his sister's the better sportsperson. "She got player of the year in soccer I was rubbish." Tumanako also played in the Bay of Plenty touch squad and captained the kura volleyball team.
During most of his secondary years Eru considered a future in zoology or robotic engineering. According to Tumanako he used to tuck himself away in is bedroom "making robot things all the time".
That was until recruiters from Whakapiki Ake, *an organisation dedicated to promoting health as a career for young Māori, came to the kura. Eru knew instantly this was the path he wanted to take.
"Through them I learnt a lot about health inequities between Māori and Pākehā. I said to myself 'I can do that as a doctor'."
He was accepted into medical school, preceded by a year studying health science.
There was, he admits, a lot of partying and not much study in his first med school years. "Surprisingly when exams came I'd somehow smash them."
Tumanako has an explanation for that.
"He studies hard not always smart while I study smart but not always hard."
After eight pre-graduation months at Rotorua Hospital last year, Eru spent two in Samoa working in intensive care. "That was a real eye-opener, it made me realise how good we have it in New Zealand."
This year he's back on Pukeroa Hill (Rotorua Hospital), presently based in the Older Persons Rehabilitation Unit but future options remain a work in progress.
"I think I may go to he opposite end of the spectrum, paediatrics interest me but I like ED (Emergency Department) work too, I'm still working on it."
Tumanako doesn't accept she's following in her brother's footsteps by heading for a degree in medicine; she didn't always want to be a doctor. First choice was a vet "but I discovered I was allergic to animals so I moved to people but when I left school I failed to get into med school. I think my family were more gutted then me." She too studied health science before commencing nursing studies.
During her three university years there were a lot of hospital placements, her stand out favourite being the Mason Clinic which specialises in the care for the psychiatrically unwell.
"I spent a lot of time in the Māori unit which has a marae at its heart, every morning starts with karakia (prayer). When patients are practising their haka they are releasing their pent-up anger, angst."
But it was a surgeon's invitation to scrub up for a couple of gall bladder operations that set the seal on her determination to become a doctor.
"I had my doubts I could do it [the operations] but they were so cool, the surgeon brought me in to assist with the action, afterwards he said 'never doubt yourself again'."
Self-doubt has never been on the Bidois' siblings' order papers, their commitment to Māori health is absolute.
Or as Tumanko puts it: "It's never been our priority to shine but to become health professionals for the good of our people, putting them before anything else."
*The Bidois siblings, along with their father, have just been filmed for a video promoting the Whakapiki Ake organisation.
Eruera and Tumanako Bidois:
Born: Palmerston North - Eruera 1994, Tumanako 1997.
Whānau: Parents Ngahihi and Carolyn Bidois, koro Tommy Bidois, his wife Raewyn Taua. Felicity Jansonius (to marry Eru on February 28).
Iwi affiliations: Ngāti Rangiwewehi, Ngāti Tahu/Ngāti Whaoa, Ngāti Pākehā.
Education: Kohanga Reo Tauranga, Te Kura o Te Koutu Rotorua. Eruera - Auckland Medical School; Tumanako - Auckland University.
Interests: Eruera - Fishing, diving, hunting, gardening. "Vegetables, I'm enamoured with the idea of being self-sustainable." Tumanako - Kick boxing "high intensity workouts solely for my fitness". "Writing in my journal." Regular walking.
On Rotorua: Both: "It's home."
On their lives: Eruera - "We are very fortunate to have been brought up here with our people". Tumanako - "It's been full of challenges and pleasant surprises".
Personal philosophies: Eruera - "Ehara taku toa i te toa takitahi he toa takitini ke: My achievement aren't those of mine alone but many." Tumanako - "If not me, who? If not now, when?"