My father left my mother for another woman. He wants us to start including her. Do we need to?

‘You can be righteously wounded in perpetuity, or you can be close,’ writes Eleanor Gordon-Smith. Painting: The Jones Family Conversation Piece by William Hogarth. Photograph: Alamy

My parents got divorced four years ago, at which point my brother and I were both in our 40s, and our parents almost 70. They broke up after my mother discovered that my dad had been having an affair. The feeling of letdown was enormous, as if our father had suddenly become this person we didn’t recognise. He had always taught us to be fair and honest, and this made us question everything.

My brother and I have made a lot of effort to keep him included in our lives since then, especially for the sake of his grandchildren. However, we’ve only had one demand – that we get to see him alone. The Other Woman still feels like the cause of the breakup of our family. I feel an enormous amount of hurt and resentment about the lies and deceit, but I’ve made a conscious effort to not wipe out his positive impact on my life up to that point.