The first book, the one that is actually titled Case Histories, explains it very well.
He grew up in Yorkshire, where his dad was a coal miner. He had great parents and a much older brother and sister. The sister was only a year younger than the older brother, but he, Jackson, was an afterthought, or change of life, or just flat out mistake or something. Anyway, they lived happily ever after until his mother died. Then his sister took care of them while working in the town. The older brother often picked her up at her bus stop. This one rainy day he did not. She reached the bus stop near her home after work, but was abducted and raped and murdered and thrown in the canal between there and their home. I think they said it was on the first anniversary of her death that the older brother could not handle the guilt any longer and he hung himself. So Jackson was left alone with his dad at something like 12 years of age. Then his dad died, and he had no other relatives whatsoever.
So he really treasures that one little girl he has.
The film also did not tell us that Binky Rain, the old woman who lived in the house with the huge garden and apple orchard behind the house the Land sisters lived in (there was an alley way between the yards and the yards were fenced, with gates) and it was her place Olivia Land was buried in, oh, and also she had all the cats, well, Binky died and left Jackson about two million POUNDS, so he is Rich. And he remains rich in the following books. Seems he was the only one who was always kind to Binky.
