DEAR DEIDRE: My brother-in-law has a mistress despite being married to my sister.

I only found out about their affair a year ago but apparently it has been going on for nearly 10 years.

No issue is too small, too large or too embarrassing. Read our personal replies here.

The worst part is my sister knows all about it but she is so proud and won’t talk about how hurt she is.

They still live together and even share a bedroom as neither of them want the children to know.

I’m 47, my sister is 46 and her husband is 49. Their children are 17 and 18.

I feel so angry on her behalf but she won’t say a bad word about her husband and simply explains that it makes more sense to carry on as they are.

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She won’t open up to me and yet every time I see her she is utterly miserable. I find it so upsetting.

I want to help her find a counsellor.

DEAR DEIDRE

My husband walked out on me and the kids on Christmas Day

SMELL ISSUE

How do I tell my father-in-law he smells?

HAPPY EX-MAS

NO ROOM AT THE INN

DEIDRE SAYS: As upsetting as this is, your best role is to support your sister and be there for her when she is ready to open up.

We can’t always assume others feel the same way as we would.

If it were your sister writing I would send her my support pack on cheating and counselling to help her see a way through this situation.

If you can find the right time it would be worth passing these on.