Never-before-seen photos emerge of David and Louise Turpin before their 'house of horrors'.

Anyone looking at a photo of David and Louise Turpin taken outside their home in Rio Vista, Texas, would assume the best of this happy-looking couple – including Louise’s sister.

“I thought their life (at Rio Vista) was perfect, just like it was when we went out there (to visit),” Louise’s sister Teresa Robinette told 60 Minutes.

“She always had nice homes and the nice cars. They were the most perfect family I ever had seen.”

But what prosecutors now allege is that the couple’s abuse of their children escalated at this idyllic property they moved into in 2000 and grew more extreme over the family’s 10-year stay.

David and Louise Turpin hadn’t always been the alleged abusers the world now knows them as today.

In 1985 they were married and by 1989 had their first child.

David Turpin's job as an engineer at the aerospace company earned him a six-figure salary the couple supported their growing family on.

By 1996 they had six children and it is around this time authorities suspect the alleged abuse began.

Still, although neighbours suspicions were raised several times over the 10 years they lived in Texas, authorities didn't discover the couple's alleged torturous treatment of their children until several years after they had moved on.

It was in Perris, California, on January 14 this year that a 17-year-old Turpin daughter escaped and alerted police to her parents' alleged abuse.

David and Louise Turpin will face 49 charges, including counts of torture and child abuse of 12 of their 13 children, at their upcoming trial. They will next appear in court on August 31.