'My sister married my ex-husband. We haven't spoken for 10 years.'

As told to Anna DeGrey

My younger sister Penny* always had a close relationship with my husband Ben*. They shared the same wacky sense of humour, they both played golf – sometimes together. And sometimes I felt a bit left out because Ben and I didn't have a huge amount in common aside from sharing a house and a daughter.

I always liked seeing Penny and Ben enjoying each other's company and once I even joked that they were more 'couple material' than Ben and myself. They both laughed at that which makes what happened later feel rather sinister. Or perhaps I was somehow jokingly projecting what was to come.

Ben and I broke up after seven years together and we were very amicable for the sake of our daughter. It wasn't nasty; it was just very sad. I feel like we did love each other but our passion had disappeared, and we were mostly just friends. In fact, we were less than friends because when I was going through a hard time after losing my job and spiralling into depression; he wasn't exactly a supportive partner.

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We decided that I'd stay in our house with our daughter who was aged six at the time, and he'd move into an apartment. We shared custody, and for a couple of years, everything was fine. I met my second husband and while Ben had told me he was dating, I never wanted details. Part of me still loved him, I guess, so I didn't really like to know about his love life. One thing we'd always had going for us in the early years of our romance was a fantastic sex life. 

Shortly after I married for the second time, Penny's marriage ended. Her husband was a nasty piece of work, so nobody was surprised when that ended. I was very supportive of her and she referred to me as her 'rock' because I helped her navigate her kids through the divorce. Penny's daughter was just a year younger than my girl and they both attended the same school. I always felt it was a good thing that my daughter had her cousin at the school, they'd sometimes find each other in the playground as they really were more like sisters. 

Yet that became another thing to haunt me as time went on.

Penny's divorce was much trickier than mine as her ex was fighting for a larger share of their house in their financial battle. Again, I was very supportive, and she also told me that Ben had given her some great advice. That was the first time I realised that my sister and ex-husband were in touch. When I questioned her she said, "Yes, we catch up every now and then."

"Why are you two catching up?" I asked.

"You know we've always been friends!" she said, quite defensively. "I shouldn't have to cut off contact from him, he was my brother-in-law."

I let that one go but a few months later, the true story came out.

Penny's daughter let it slip to my daughter that her father, Ben, stays over at their house sometimes.

When my daughter mentioned it, I immediately felt a cold shiver down my spine. That's when I knew that something was wrong.

I didn't question my daughter further, aside from asking her if my niece likes seeing Ben at her house. "Yes, she likes him a lot," my daughter replied.

I waited until my daughter was at school, and I phoned my sister immediately. I've never been backward in coming forward to ask her if it is true that Ben has 'sleepovers' at her place. Penny was silent for long enough to make me realise that she was about to break bad news.

"I'd better come over," she said.

That's when she told me the truth, that she and Ben had been dating for several months and were waiting for the right time to tell me.

I couldn't believe it! How could my own sister – a sister I adored – do this to me? And how could she do this to our daughters? 

It's been almost 10 years since Penny and I stopped talking. I miss her very much but I am still devastated that she is with the father of my daughter, a man I once loved. I'm still in touch with Ben and he has tried to convince me to talk to Penny but I'm not ready yet. If she apologises to me for the drama she's caused, then maybe I could forgive her. But not yet – I don't know when I will ever be ready to see her again and there is no way I ever want to see her with Ben, I don't think I could handle that.

The author of this story is known to Mamamia but has chosen to remain anonymous for privacy reasons.

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