His father, Warren Snr, is director at Auckland's Southern Cross College, while Rona is the head of guidance and well-being at the school.
Warren Snr had travelled to Germany with another son, Tane Waetford, to bring Warren's body home.
A spokesperson from his German employer said Waetford was "extremely passionate about climate change and working for the environment".
He had joined the company as an expert on climate change and ways of reducing emissions caused by deforestation.
"He was not only a very good lawyer, but also a positive person that settled so well into our organisation in a very short time," the company said on its website.
"He was a valuable addition to our team and showed his extraordinary personality in every situation."
Warren had worked in top positions around the globe including at the United Nations Framework Convention on Climate Change, at the Ministry of Foreign Affairs and Trade and at the New Zealand Permanent Mission in Vienna.
Rona said her son had been very modest about the top positions he held around the world.
"He very much downplayed the part he played on the international scene," Rona said.
"When he would settle in these different countries for Apec meetings, he would say, "I'm just doing stuff" but we are finding out he was globally recognised as an outstanding environmental lawyer.
"That was his signature, he was very, very humble."
Tributes from Korea, the Netherlands, Asia and Canada described a fun loving, dynamic man with huge talent.
The wife of New Zealand diplomat Tia Barrett said her late husband held Warren in the highest regard.
"He supported you and all those we worked with, but to hear this news of your passing has brought sorrow to me. You had so much to offer the world and my condolences to all your whanau and all those you have touched on your short journey."
Another described Warren as "a breath of fresh Aotearoa air" for the United Nations.
One of seven boys, Warren was fluent in Maori and German and had degrees in the Arts, Law, Maori studies and International Law from Auckland University, and a Master of Laws and degree in International Law from Amsterdam University. His body is expected back in New Zealand later in the week.