Dickens married Catherine Hogarth in 1836 and they had ten children together. In turn Catherine's sisters Mary and Georgina joined the household as was customary in that time. Mary became ill and died. Georgina remained in the household after the separation to look after the children, retaining a fierce loyalty to Dickens.
Who knows what precipitated the growing coldness between Charles and Catherine. It was probably partly due to their differences in temperament. Catherine was a homebody, an introvert and lacking in Dickens' energy and enthusiasm for everything he encountered. Dickens craved novelty, excitement and intellectual stimulation. Catherine could not compete. Then too, bearing and raising ten children would have changed her from a trim and lovely young woman to a matronly and domestic homebody. She had far more demands on her time and emotion than did Charles.
Into this situation entered Ellen Ternan. She was 18 and Dickens 45 when they met. He spotted her performing in Haymarket and fell in love. He arranged for her to act in his plays and they began their thirteen year affair.
Catherine discovered the relationship when she inadvertently opened a package from a jeweller meant for Ellen. After 22 years of marriage she took one of the children and left. The other children remained in Dickens' custody cared for by Catherine's sister Georgina.
Rumours of the affair started after the separation, rumours which Dickens vehemently denied, even taking out spots in newspapers to proclaim innocence. During their long relationship, Dickens arranged residences for Ellen under false names so they could be together in secrecy. She sometimes travelled with him along with her mother, but generally they tried to keep the affair out of the public eye.
Some of the characters in Dickens' novels are believed to be based on Ellen, such as Estella in Great Expectations.
Dickens died in 1870. In his will he left a thousand pounds to Ellen. The managers of his estate managed to keep his affair with Ellen quiet until the death in 1933 of his last remaining child.
In spite of the separation and affair and the loss of his love, Catherine remained loyal to her husband. Just before her death she handed some old letters to her daughter with the instruction "Give these to the British Museum that the world may see that he loved me once."