Sisters of Mercy and biological sisters Diana and Lorraine Thomas have no regrets over committing their lives to the Lord.

Diana and Lorraine Thomas have no regrets over never marrying or having children or even their unlikely career choice.

They both have worn wedding veils and still wear wedding rings. They are biological and spiritual sisters - married symbolically to Jesus.

Along with two other Sisters of Mercy who are in their 90s, Sister Adrian and Sister Celine, they live in the 12 bedroom convent in Timaru built in 1982 which has no double glazing or ensuites.

JOHN BISSET/STUFF Lorraine, 82, and Diana Thomas, 76 are the youngest of four nuns still living at the convent in Timaru.

They're among a dwindling number of women who chose to devote to faith and church.

READ MORE:

* Sister Pauline O'Regan was a writer, teacher and community leader

* Nuns speak out against abuse in the Catholic Church

* Life as a Kiwi nun in an age of refugees and Netflix binges

In the Christchurch diocese, there were 486 nuns in 1970, 190 in 2000, and just 100 in 2016.

Massey University Emeritus Professor of History Peter Lineham says up until the 1960s, at least one member of every Catholic family was expected to become a nun or priest, usually when they were entering their teenage years.

But changing family dynamics, the loss of power of the church, and the many options available to serve God in other ways had seen new applicants drop away.

Lineham says Catholics used to live in a separate world with their own schools and sports teams, with nuns and priests having a huge influence on those young minds.

Now schools were integrated and most of the teachers were no longer nuns or priests and the ones left were of "a different age".

JOHN BISSET/STUFF Lorraine and Diana Thomas say the Church will always have an important place in society.

"Those people who have a deep calling to serve God find the opportunity to do so through international services such as Volunteer Service Abroad," Lineham says.

The Sisters of Mercy religious order was the first to come to New Zealand in 1850. Founded by Catherine McAuley in Ireland in 1831 its focus was on sheltering homeless women, tending the sick and dying, and educating poor girls.

The number of sisters in the Ngā Whaea Atawhai o Aotearoa Sisters of Mercy New Zealand has roughly halved since 2008. But the sisters do not fret about their order dwindling away after all they really believe it's up to God what happens.

Sister Diana is the youngest at the age of 76. Her and Sister Lorraine's job trajectories were influenced by the nuns who taught them at the Catholic primary and secondary schools they attended in Christchurch where they grew up.

Sister Lorraine, 82, never wanted to be anything else and recalled as a child playing by wearing a tea towel on her head, with a ruler in hand teaching Ginge the cat whatever she thought was an important lesson for the day.

"Our parents weren't surprised, all I had ever said was I wanted to be was a nun," Sister Lorraine says.

JOHN BISSET/STUFF The Thomas family pictured in the early 1960s, from left, Phyllis (mum), Robin (brother), Sister Lorraine, Goeff (dad), and Sister Diana, and Annette (sister). Lorraine was a fully professed sister and Diana had completed her reception ceremony six months earlier signified by her white veil.

It was Lorraine's reception ceremony in 1955 when she was 18, that prompted the then 12-year-old Diana to decide to join the Sisters of Mercy order too.

She's never looked back since.

Held in the big old convent that used to sit where the Roncalli College rugby field is now in Timaru, Sister Lorraine and a dozen Irish women dressed in white veils and white dresses, symbolising brides of Christ and made a public commitment to follow Jesus.

Three years later they took their first vows, then after another three years their final vows, receiving the ring which symbolised their marriage to Christ.

The experience made a big impact on Sister Diana.

One of Sister Diana's teachers was looking at the photos from the first ceremony and asked her if she would like to be a nun.

"I said 'yes'."

It was not until she had worked in a secretarial role for a year after leaving school that she felt ready to join.

Walking away from her first boyfriend was not hard, she says, as it was not a serious relationship.

One of her favourite teachers at St Mary's Secondary School in Colombo St made her a cashmere habit which she treasured.

She describes her calling from God as a sense of inner peace, knowing it was the right thing to do, knowing it was her purpose.

JOHN BISSET/STUFF Sister Diana Thomas at her reception ceremony in 1955 at the old Sisters of Mercy Convent in Timaru. One of the stages to go through to becoming a nun.

She became a qualified teacher in the early 1960s.

She taught on the West Coast as a primary school teacher and then moved to Timaru in 1969 taking on responsibility for the boarders, teaching home economics and religious studies at Mercy College. It was renamed Roncalli in 1982.

Nuns taught at all the Catholic schools then but that role has since been taken over by lay people.

"It's the sign of the times," Sister Diana says.

Two years later she moved to Christchurch and worked at Ka Wahine ki Otautahi Trust, a house for former women prisoners to rebuild their lives at Mary Potter Home and Hospice.

On her return to Timaru in 2003 Sister Diana looked after the running of the convent and the welfare of the eight sisters living there and the three in rest homes nearby.

One of the highlights of her career was working at a retreat as a spiritual director helping participants deepen their relationship with God through prayer and reflection.

JOHN BISSET/STUFF A statue of Mary mother of God at the Sisters of Mercy Convent chapel in Timaru.

Sharing reflections and encouraging others is part of Sister Diana's current spiritual companion role with members of St Vincent de Paul.

She is still in charge of the running of the convent and its grounds. One of the other sisters recently shifted into a rest home. Retiring is not on Sister Diana's radar.

Sister Lorraine plays bowls for fun while in her spare time Sister Diana enjoys listening to Kim Hill interviews and reading anything by her favourite author John Grisham.

"He's (Grisham) not into sexy things but writes a jolly good crime/detective novel."

If a movie takes their fancy the sisters will go out to see it. It's been a while since one did.

People feel they can confide in the nuns. The sisters are non judgmental about others' belief systems and don't appear to try and convert anyone to their way of thinking.

Keeping other people's wellbeing in the forefront of their minds is how they express their Catholic spirituality.

The sisters have lived together since 2014 when Sister Lorraine was diagnosed with macular degeneration and could no longer work in the roles she had instead helping with the laundry and dining area at the Timaru convent.

All the sisters read the Bible daily to further their relationship with God.

ALDEN WILLIAMS/STUFF The Timaru Sacred Heart Basilica is where the Sisters of Mercy usually worship but it is shut for maintenance and strengthening work. (File photo)

"God is a loving presence. There are so many little signs and situations that happen. I find myself saying 'thank you God'. I never feel alone," Sister Diana says.

Sister Lorraine describes God as a faithful friend. Sister Diana's favourite words in the Bible are "be not afraid" , which is in the Old and New Testaments in different scenarios often when God is trying to reassure someone.

The old black habits gradually changed in length and look in the 1960s and 70s. Then colour was introduced. Nuns moved out of the habit in the 1980s and 90s now there are no uniforms which the women claim was a sensible change as the black habits were often uncomfortably hot to wear.

Sister Diana did not find the switch difficult, embracing choosing her own outfits while Sister Lorraine found it a bit strange at first, but knows what she likes now.

"In some shops I wouldn't touch any of the things they have," Sister Diana says.

Other aspects of modern life sadden them, the number of broken marriages and seeing couples on their cell phones instead of talking to each other.

Sister Diana only carries an old cellphone when she drives to Christchurch in case of an emergency.

"That's simplicity."

So how does a woman married to Christ cope with temptation?

"I go through discernment and think, 'is that meant to be part of my life'?" Sister Diana says.

The sisters do not expect there will be women priests in the Catholic church in their lifetime but Sister Diana is fine with anyone who would seek that position though it would not be something she would want.

She applauds the head of the Catholic Church, Pope Francis for abolishing the name suppression of priests who abuse and issuing a new canon law that forces church officials to report abuse charges.

She does not think it is necessary to change the stance of priests not marrying as she does not see that as a way of reducing cases of abuse.

As far as the future of the church they have devoted their lives to goes, Sister Diana says it is in God's hands and will likely continue to focus on justice, truth and the wellbeing of people in need.

"There will always be a place for church in society," Sister Diana says.