My sister, who is married and a professing Christian, is having an affair with a married man. She hasn’t had any intimacy with her own husband for the past decade due to his longstanding illness. I might have the courage to tell my sister’s husband about the affair if it wasn’t for our parents. They are likely to react very angrily and cut my sister out of the will. My sister keeps excusing what she is doing due to grace! She says I can’t tell her anything that she doesn’t already know or hasn’t thought of. I feel very bad knowing what I know but don’t feel I should spill the beans.

You are in a horribly difficult situation and so is your sister. The bottom line is that I don’t think this is your information to tell. My hunch is that God’s guidance is in your conscience which is telling you that you shouldn’t ‘spill the beans’. It is your sister who has got herself into this web and it is her responsibility how she handles it. If you tell her story, you will create even more mess and will become responsible for some of the consequences. The reality is that this is her life, not yours, and we all stand accountable before God for our own actions.

What you can do is continue to seek to influence her and hold out the option to her of investing in her marriage. She also needs your support. It must be a very unhappy situation for her to be in: living in a low love marriage and constantly facing separation from the person she is giving her heart and body to.

The ideal would be to revive her courage to change her marriage. You can also seek to influence your brother-in-law, without telling him of the affair. They both need to talk about how it is affecting her that they have not been intimate for all those years. You can encourage him to ask her more about this. Without knowing more about his ‘long-standing illness’ it is hard for me to be specific, but I have counselled many couples where severe medical conditions have led to them abandoning sexual intimacy. However, in my experience, it has always been possible to rebuild some level of sexual intimacy within the constraints of what is physically possible.

It sounds like this story has the capacity to split your family and therefore needs to be handled with great caution. It is no wonder your sister is holding back on facing the consequences of her love life. Maybe what you can do is give her a constructive sounding board to think through her future and understand her past.

I am wondering if you are able to go beyond the heavy handed reactive approach of your parents and give her a greater complexity of love in this situation. It’s not so much about telling her what she knows but currently cannot do, as hearing where and why she is stuck, so that she can gradually find a way through that she can commit to. There will be very few people she can talk to due to her need for secrecy, therefore recognise you could offer her an invaluable outlet to process her dilemmas. You can’t take her free will from her, but you can challenge, comfort and support.

I hear the agony for you in knowing what you know. Often in these situations the pain we feel is multi-layered and we get stuck in it due to muddling the various causes of our own distress. Do distinguish between the different pains that you feel: some are more about empathy for each of the people involved. Realise that it is not yours to feel their lives for them. Let your empathy only extend to the places that enable you to support them constructively. Some of the pain of ‘knowing what you know’ is false responsibility. Hand this over to God and the people involved. It is not yours to carry. Focus on what you can do to bring good and let go of what you can’t.