Jim Alexander may be passionate about what he does but he is not sentimental.

The inventor of Family Functional Therapy, the most widely applied proven model for helping adolescents living in highly dysfunctional homes, can take a step back. He examines the functions of human behavior. He knows from experience that people do strange things for a reason, and it is better to focus on what’s behind such behavior.

But his interest in the way families function stems from his own fragmented childhood. Born in Tulsa Oklahoma in 1941, his father was stationed there, waiting to be called into action in the Second World War. He eventually went and never returned to his family, “He came back from the war”, Alexander clarifies, “but he didn't come back to us”.

The crisis sponsored a series of moves around the country, to the paternal family home in North Carolina, and eventually to New York.

"I had two siblings”, Alexander says. “They had different fathers but we share a mother. People can deal with life's events in obtuse ways but kids can get screwed up. My two siblings struggled with substance abuse. Their experience was a stream of inconsistent and impermanent father figures. So what else would you expect?"

Contemporary commentators might question the errant parenting of Alexander's mother. But he takes a different slant. He says: "She was a good Southern woman. She was an early version of a feminist. She worked: she was the music director of a radio station. But she was born 40 years too early. She was great at what she did but hopeless at relationships. She had no sense of continuity of relationships."

It was not always a lot of fun but it was fertile ground for learning for a boy who would go on to change the way in which we think about adolescent behavior and help society use family life as a mechanism for intervention.

"I know from growing up that relationships are not 'right' or 'wrong'”, Alexander says. “It also pointed out to me that the whole business of entering and leaving relationships is extremely complicated. It’s a part of family life. Babies are born. Parents divorce and re-marry. Eventually they die. Children leave the family nest. There is a lot of coming and going.”

As will be seen in tomorrow's edition of Prevention Action, once he left home, Alexander kept on going. From university to university, sitting at the feet of giants, applying hard won experience to the business of improving family life.

But when it comes to his own family stability has been the watchword. He and his wife Mary Beth have five children, and five grandchildren, aged between three and 14 years. One of the children lives in Europe but the rest live close by in Salt Lake City.

He puts his successful relationship to Mary Beth down to their differences. "I am over the top noisy and I cannot stop my brain from trying to work everything out,” he explains. “She is more intuitive, aesthetic, and really understands things that are often beyond me. She is a designer. She brings her functionality to questions of color, me to questions of family life. Let’s not get this out of perspective here. We make each other crazy, of course, but it’s a successful relationship".

And the father who went away from war never to return to the family home? He re-married and when he died his wife called Alexander and he learned what he needed to know to explain the flight several decades earlier.

"She said he was a good guy. He was quite basic. Very bright but quite basic. But he just didn't have the resources to deal with the intense craziness of mum. When he went to war he must have felt the relief. Such a relief that he couldn't bring himself to come back".

• To be continued in tomorrow’s Prevention Action.