But in between Powell's dark adolescence and grisly murder-suicide, there was a time of light and love with Susan Powell, those close to the couple said.
"Susan and Josh got married, and he seemed to have come around pretty well," Josh Powell's older sister, Jennifer Graves, told "20/20." He seemed to be in a pretty decent place. And I had really high hopes for their marriage, that it would be a successful, happy, good one."
PHOTOS: The Powell Family
Josh Powell and Susan Cox, each the children of churchgoing families, met at a church function. They were engaged when Susan was just 19 and married in 2001.
"At the very beginning they were, you know, happy, holding hands, hugging, kissing each other," said Susan Powell's sister, Denise Cox. "You thought [they were] a perfect couple, a very happy couple."
Those who knew Susan Powell said she was warm and open -- qualities that endeared her to her neighbors in West Valley City, Utah, where the couple had settled several years after their marriage. Josh Powell was not as popular.
"We all love Susan and we tolerate Josh because he comes along. It's part of the package -- that's how most people felt," former Powell neighbor John Hallewell told "Nightline" recently. "She was always worrying about other people, where Josh was always the opposite. He was only ever concerned about himself, which made things, sometimes, a little difficult."
Susan Powell's parents, Chuck and Judy Cox, found it strange when Josh Powell refused to drive his wife to the hospital when she went into labor with their first child, insisting that her parents take her instead because he had to finish something.
He finally did show up at the hospital two hours later.
"And what he had to do was, he wanted to back up his hard drive before he left," Chuck Cox said.
Graves said she watched as her younger brother, Josh Powell, "faded out."
"As the, the years progressed, I saw him go downhill, you know, slowly at first," she said. "He kind of just regressed a little bit. And then the last few years before Susan's disappearance, it just seemed to accelerate and he seemed to get worse and worse."
Friends said Josh Powell became so controlling of his wife, it became legendary among those who knew them. She had to get his permission just to use the family car and had to follow a strict procedure in order to spend any money.
"He would give Susan an amount of money -- and on grocery shopping, he also had a spreadsheet that she was to look at through ads and find the cheapest price of things," said a friend, Michelle Oreno. "When she went shopping, she came home and she had to enter every single item into that spreadsheet. And if she spent more than a couple of cents more on a can of beans, Josh would really yell at her and get angry."
Josh Powell wouldn't even let his wife spend money on socks, insisting she knit them instead, said Denise Cox.
She said her sister considered leaving Josh Powell but didn't do so for fear of what would happen to the couple's two children, Charles and Braden.
"When I told her to leave with the kids, she told me that he had told her, 'Over my dead body will you have those boys. They're mine,'" Denise Cox said. "The boys were a possession to him. They were his possessions."