The couple spoke to OK! magazine about how it feels to be first-time parents, and revealed details of what Kelvin described as a 'traumatic' birth.
'I never imagined I could be so obsessed with a little person,' Kelvin said. 'I knew I'd be hands-on, but fatherhood is incredible.
'I can't imagine life without her now.'
Liz added: 'Marnie's incredible, she's such a little angel. She sleeps really well and she's a really calm baby.'
Kelvin with wife Liz and their daughter, Marnie Molly Fletcher
Former Emmerdale actor Kelvin also opened up about his daughter's arrival, praising his 'brave' wife after an exhausting 30-hour labour and complicated birth.
'Liz had to have a blood transfusion, but she was so brave,' he said. 'Seeing Liz go through a traumatic birth made me look at her in a different light.
'I have utmost respect for her and my love for her has gone up tenfold, and in a different way too.
Kelvin added: 'There's a bond that's created instantly and I'm indebted to Liz forever for bringing Marnie into the world. It's a miracle.'
The couple first announced the arrival of their beautiful new daughter on Kelvin's Twitter, posting: 'Our hearts are filled with love. She's the most beautiful little thing I've ever seen'
Our hearts are filled with love. She's the most beautiful little thing I've ever seen ð— Kelvin Fletcher (@kelvin_fletcher) September 5, 2016
eliza_marsland's photo https://t.co/0FdteZro9w
Liz also revealed the news, sharing a picture of a bouquet of pink flowers on her Instagram page. She captioned the photo: 'Everything pink for the little cherub #bestfeeling in the world!'
The couple announced their pregnancy last Christmas. Kelvin revealed to OK! magazine that Liz actually became pregnant on their wedding night in November.
He said: 'We're pretty sure Liz fell pregnant on our wedding night. We then flew to Rome for three nights. Little did we know, there were three of us on our honeymoon!'
The new dad added: 'The day I found out Liz was pregnant and our wedding day were the most amazing days of my life.'
However, Kelvin and Liz decided to keep the sex of the baby a secret, so the arrival of a daughter will have been a huge surprise to the couple as well as friends and family.
Liz appeared on Loose Women just three weeks before giving birth, saying she'd been keeping Kelvin close by in case the time comes. She told the panel:
'I've become Kelvin's side-kick in case anything happens. I'm just following him around!'
The couple married last November after dating for nine years. They decided they wanted to wait until they were in their 30s to start a family so they could enjoy their twenties together as a couple.
We're used to seeing Kelvin as Andy Sudgen in Emmerdale, but he recently left the show after appearing in the soap for 20 years. But it seems to have come at a good time, as he'll be settling into his role as a dad instead!
Congratulations to the new parents!
Read the full story in this week's OK! Magazine - out today