Stepfathers 

Researchers from the University of East Anglia and the University of Essex have published findings from a study into child homicides by stepfathers. The report found that both youth and living apart from the child were more significant factors in determining the risk of child homicide by a father figure than being a stepfather. The research suggests that previous findings, which indicated that stepfathers were far more likely to kill their children than birth-fathers, could partly be explained by the relative youth of stepfathers and records labelling a range of non-residential perpetrators as stepfathers regardless of their relationship to the child.

Source: Child homicides by stepfathers: a replication and reassessment of the British evidence (PDF)

Further information: BBC