Elizabeth Jane Flores, 41, from Cleveland told Daily Mail she had not seen her sister in over 19 years, and while she did keep in touch via telephone, Turpin refused to invite her over to her home and never let her speak to her nephews or nieces.
Flores revealed, 'Something didn't seem right about her parenting but never would I have expected it to be like this.'
'We have been so worried about them because it's been so strange but there was nothing we could do,' she continued. 'They wouldn't let anyone visit and we didn't know their address. I haven't seen her in 19 years. We would talk on the phone from time to time, but every time I would ask to talk to her kids, she wouldn't let me.'
Flores even reveals to Daily Mail that their mother had flown out to visit the couple, but they had refused to give them the address.
'She never let us talk to her kids. She wouldn't even accept my Facebook request. We all wondered what was going on,' Flores shockingly revealed. 'My parents booked several flights to go see them but when they got there they wouldn't tell them where to go and my parents left crying every time.
'They died before they got to see them again. It's just heartbreaking and I'm so embarrassed about all of this.'
The couple were arrested and charged with torture and child endangerment on Sunday after their 17-year-old child escaped and fled their California home.
Their thirteen children, aged from two to twenty-nine, were taken to hospital immediately.
Police have since revealed that all siblings were desperately malnourished and pleaded with officers for food and water. It is not known how long their parents kept them chained and shackled in the home.
Wendy Martinez, 41, who lives in a home behind the couple's property, told Daily Mail she saw four of the children kneeling in the front yard late at night at the end of October.
She also revealed that when she called out to the four children it appeared as though they had been instructed not to respond.
Martinez told Daily Mail, 'It was about 9pm at night and we came around right here and at the gate, we saw four children inside. They were on their knees, four little kids, and they were just rolling on the grass. It was odd at that time of night.'
Martinez added: 'It's weird – you never know what's going on. They've got three cars and that [mini]van. They move it, there's no cobwebs.
'They're mobile. I don't understand why they would wait so long to say something. Looking at their pictures, they seemed like the perfect family.'
Police found that some of the children had been shackled to their beds and were being held in 'a foul-smelling room'.
State records reveal that David Turpin home-schooled his six children at their address, calling it Sandcastle Day School.
David's parents, James and Betty, told ABC News they were 'surprised and shocked' at the news.
The couple are being held at Robert Presley Detention Center east of Los Angeles and their bail has been set at $9million. They will appear in court on Thursday.