However, she subsequently discovered Roberts and his wife were living apart although they remained in daily contact.
Roberts was in Alison St, his wife in Homedale St.
When he made the offer to take the twins she was stressed, emotionally unwell and had had a falling out with her mother with whom she'd been living after the twins' six-week premature birth. Their delivery had been by caesarean section.
She said while she was receiving treatment and trying to get herself "back together" she considered adopting the twins to Roberts, who she'd met through a friend.
Before the babies went to live with him she had regular support visits from Tipu Ora and Plunket but didn't know if these continued once the boys were in Robert's care.
Roberts brought the boys to see her about once a week when she was living in a Te Ngae flat and she visited them about three times in Alison St.
"Shane told me his wife wasn't happy with me seeing the twins because she was raising them as her own," Stephens testified, adding CYFS had become involved.
A few days before Karlos' death Roberts invited her to stay at Alison St, he wasn't there at the time and the house was without power. Roberts told he'd top up the pre-paid power supply but this hadn't happened. Without it she was unable to charge her cellphone.
She told Crown solicitor Amanda Gordon she'd agreed to stay at the Alison St house because Roberts said he'd bring the twins around to see her.
They day after she moved in she spent about two hours with them. For most of the visit she cuddled Karlos because he appeared unwell, displaying flu-like symptoms.
"He was clingy, grisly, tired and very warm, he didn't want to eat, he just wanted to be held."
Questioned by Gordon about her twins' personalities Stephens said Karlos was a cuddly child while the other twin Hosea was more bubbly and more active.
She told of asking Roberts to take Karlos to the doctor and he'd agreed to after going to see somebody.
Early the following morning she'd been woken by the sound of a car skidding, followed by kicking at the front door. Roberts burst in saying Karlos was in the car and not breathing.
"I said 'what happened?' He mumbled and said he didn't know."
She described lifting Karlos out of the front seat where he was lying unresponsive and wrapped in a blanket.
"I said we are going straight to the hospital, he [Roberts] wanted to call an ambulance, my cellphone was flat. I said there was no time for that, I was in shock."
Roberts asked her who was going to drive, "I said you are, I am going to sort this mess out".
In her opening address Gordon told jurors they would hear on their way to the hospital Stephens had been willing her son to live but he was unable to be revived.
Although there were no obvious signs of outward injury a post mortem revealed bleeding across the surface of the baby's brain. He also had extensive eye bleeding.
"He ultimately died from a lack of blood and oxygen to the brain," Gordon said, adding what caused the extensive trauma to Carlos' head remained unknown.
Roberts' lawyer Max Simpkins didn't make an opening statement.
Six men and six women were selected to try Roberts. The trial is set down for two weeks with Justice Matthew Muir presiding.
Stephens is scheduled to continue her evidence tomorrow.
