Four adults and three children are dead; two children are in hospital. This is the grim tally from just two incidents of extreme domestic violence committed in ordinary British homes in the last few days. Such apparent murder-suicides have a profoundly shocking effect on family and friends, who are left asking painful questions, but they also underline the need for the Government's new consultation on how domestic abuse is understood and handled in this country.

It is only a week since a former police inspector, Toby Day, murdered his wife and youngest child and wounded two older children before killing himself. Last weekend, another father, Richard Smith, like Day, aged 37, stabbed his wife and two sons before setting fire to a bedroom and dying of smoke inhalation. We've since seen a heart-rending photograph of Smith holding his baby son Aaron, while his wife Clair places a protective arm around their elder son, nine-year-old Ben.

They look like the perfect family, and it's far from unusual for stunned neighbours to talk about men who appeared to live for their wives and children. Clearly this impression of normality cannot be right, but it also shows that the understanding of what constitutes domestic abuse is too limited. Physical violence is just one of the ways that abusive men (and some women) maintain control over their partners, as social workers and refuge staff know from working with victims. Men who "live for" their families often have an abnormal need for control; when they experience stressful events, such as losing a job or discovering an affair, they may decide that their families would be "better off" dead. By then, their partners may have endured years of controlling behaviour – shouting, bullying, restrictions on what they are allowed to wear – without recognising that the situation could escalate into lethal violence.

Yesterday, in a welcome development, the Home Office announced that its consultation will focus on whether the definition of domestic abuse should be widened to include "coercive control". Obviously the signs are less easy than bruises for outsiders to spot, but it would be a significant step in changing how victims themselves think about abuse, and hence their readiness to talk to someone about it.

The consultation will also look at expanding the definition to victims below the age of 18. The Director of Public Prosecutions, Keir Starmer, recently warned that 16- to 19-year-olds are now the group most at risk. The murders of two families in a single week are extreme and unusual events. But whenever one of these tragedies occurs, it always has a long history. No matter how difficult the circumstances, adults in happy, healthy relationships do not suddenly slaughter their nearest and dearest.

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