Charlie said plastic, which does not break down, was dangerous to marine life in the harbour.
To illustrate his point, he had drawn a picture which showed 'parking ticket plus whale means a dead whale'.
He said if they continue finding the tickets at the rate of two a week, that would be 104 a year.
"If a whale ate those it would mean 104 dead whales, which is quite bad.
"We thought it would be better for the environment if the parking tickets were made of paper rather than plastic."
Mayor Sheryl Mai thanked the brothers for bringing the issue to the council's attention and told them there would be an investigation.
"You've given us some great ideas about how we can do better for the environment," Ms Mai said.
The council's roading department would be notified and would investigate, reporting back at the next council meeting.
Ms Mai said she hoped there was a more environmentally-friendly alternative the council could use.
"There's an expectation from councillors that we are presented with alternatives."
Senior asset engineer Greg Monteith said the tickets were made of paper and had a thin plastic coating over them, making it difficult for them to break down.
In the past, they had been made of paper but there were problems with the paper jamming in the machine, and the print on the ticket fading when the ticket was left on a dashboard in the sun.
He said there are about 60 machines in Whangarei which dispense the tickets.
Mr Monteith said the council did not want the tickets ending up in the harbour.
"If we can change that, we need to be looking at it."
Mr Monteith said the roading department would look into options for different materials and different methods of payment.
Ms Mai said in the meantime, she encouraged people to use mPark, a mobile app which allows people to pay for their parking online, eliminating tickets.