David Bain's future mother-in-law says she is "delighted" to welcome him to the family.
Bain proposed to his girlfriend Liz Davies, a teacher at Cotswold School in Bishopdale, at the weekend.
Miss Davies was not talking publicly yesterday about the engagement, but her mother Carolyn Davies said: "We are all delighted."
Carolyn Davies is a long-time Bain supporter, having visited him in prison and billeting him during his second trial in the High Court in Christchurch, making his lunch every day.
Bain, 40, was convicted in 1995 of murdering his family and spent 13 years in jail before being he was acquitted in a 2009 retrial.
He is currently waiting to hear if he will be awarded compensation from the Government for his false imprisonment.
Miss Davies has been showing off her engagement ring to colleagues this week who have rallied round her since the news broke in the media yesterday.
Carolyn Davies was baking at her Casebrook home, near where her daughter teaches, when approached for comment yesterday.
She declined an invitation to speak about her daughter's engagement saying: ``It's very private.''
However, she couldn't hide her happiness at the decision for the pair to tie the knot.
``We are all delighted,'' she said.
Yesterday, parents picking up their children from Cotswold School were overwhelmingly supportive of Miss Davies.
Eight sets of parents - mothers and fathers - gave their backing to the engagement, with most saying Miss Davies was an exceptional teacher. All declined to be identified.
One father summed up the feelings of most by saying: ``I've got no problem with it at all. It's none of my business.''
Online message boards were generally supportive of Bain and his future wife.
Two parents of Cotswold School children waded in on Trade Me community board with support for Miss Davies, who is
also high up in the Canterbury Girl Guides regional management.
One wrote: ``This is my son's teacher and I can assure you she is a wonderful teacher. Private life is private.''
The school itself was tight-lipped over the news.
Teachers were posted at the gates after school today and told news media to move on.
``At the school, we have no comment on personal matters,'' said principal Stephen Harrison.