Annie Jane Schnackenberg, a Wesleyan missionary, temperance and welfare worker, and well-known suffragist, was one of Kate Sheppard's right-hand women.
"Annie devoted her life to social justice," her great-grandson John Schnackenberg said.
Annie was also vice-president of the National Council of Women New Zealand in 1896, and national president of the Women's Christian Temperance Union from 1892 to 1901.
John, his wife Catherine, and their two daughters Madeline and Charlotte will lead Saturday's street parade.
Joining them will also be John's famous older brother Tom Schnackenberg, of America's Cup fame, and their sister Mary, who will be accompanied by her guide dog.
John said the family has always known of his great-grandmother's political background.
"But the importance of Annie's role probably didn't really hit home to me until I saw her name listed among five or six others on a commemorative mosaic in Auckland 25 years ago."
He said he was "immensely proud" to be asked to help honour Annie and the other suffragettes who battled so hard for women to be able to have a voice in their own future.
Former Prime Minister Helen Clark, who was the country's first elected woman prime minister when she took office in 1999, will be the guest speaker.
Event organiser Nicky Austin said this was a free, fun event that everyone was invited to attend to celebrate a significant turning point in the rights of women.
"It definitely adds a great touch to the day to have the Schnackenberg family leading the parade, and there will also be a number of ladies taking part who are direct descendants of women who signed the original [right to vote] petition," Austin said.
"There is a huge amount of buzz in the town and people are quite excited about the Suffrage 125 event, and having Helen Clark as our guest of honour is amazing."
