The legal definition of domestic abuse:

Domestic abuse involves any single incident or pattern of conduct where someone’s behaviour towards another is abusive, and where the people involved are aged 16 or over and are, or have been, personally connected to each other (regardless of gender or sexuality).

’Personal connection’ means the individuals concerned:

• are due to be, are currently, or have been, married or civil partners to each other
• are, or have been, in an intimate personal relationship with each other
• are, or have been, parents (or had a parental relationship) to the same child
• are relatives (the Act gives further definitions of ‘relatives’)