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DEAR DEIDRE: My sister is happier than she’s ever been before; she’s got a great job, a boyfriend who everyone loves and - the real cherry on the cake - she recently told me they’re going to start a family.

But what she doesn’t know is that her boyfriend is keeping a dirty little secret and now I’m so torn over what to do with the information.

I’m her younger sister and one of my colleagues recently shared photos of the bloke she’s in a situationship with.

She’d been boasting about the amazing sex they’d been having for weeks, saying she’d never met anyone with so much energy.

Apparently this bloke couldn’t keep his hands off her.

She loved telling me about how he’d throw her around the bedroom and get her into positions she didn’t even know existed.

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It was all fun and games for me and I looked forward to her updates until she sent me his social handle.

Looking him up I felt sick as I saw photos of them draped over each other and plenty of images of him posing with his top off. His smug face was revolting.

It was lucky I wasn’t with my colleague at the time or my reaction would have given him away.

He’s created a completely different social media persona and has been having this fling for a couple of months.

I’m 26, and my sister and her boyfriend are three years older than me.

All while my sister has been going on about how amazing he is and getting excited about their future.

Spotting the signs your partner is cheating

They don’t live together as yet but have started flat hunting.

I feel like some kind of dark angel and wish I didn’t know any of this.

How can I burst her bubble? She might even be pregnant and I’d be destroying their future family.

And I like my colleague - as far as I know she doesn’t even realise the truth about my sister’s boyfriend.

What can I do?

DEIDRE SAYS: You won’t be destroying anyone’s future. The responsibility for that lies 100% with her boyfriend.

Your sister is on the cusp of making a much bigger commitment to this man, first of all moving in with him will tie them closer together and if she starts a family with him, not only are innocent children being brought into this dishonest dynamic but she will have this man in her life forever.

Now is the time to act. You can’t pretend you don’t know. Far worse for your sister to find out later on that you knew all along that he was cheating.

Talk to her boyfriend and let him know the game is up. Insist he comes clean with your sister and give him a short deadline, time is running away and she deserves to know sooner rather than later.

If he doesn’t come clean, I’m sorry but I think it’s best if you tell her what you know.

Give her the knowledge and support her as she learns the reality of his commitment.

Once your sister knows you can also let your colleague know. She is innocent in this mess also.

My support pack Cheating Can You Get Over It? will help your sister work out if she still wants to salvage her relationship.

Dear Deidre’s Double Lives

From secret affairs to hidden addictions, double lives regularly surface in Deidre’s inbox.

One woman is involved in an intense affair with her child’s teacher, torn between the passion of the secret romance and maintaining her family life.

Another reader admits to repeatedly cheating on her loving boyfriend, compelled by a need for attention and desire, while living a seemingly normal relationship.

And a third man’s married double life came crashing down when his mother discovered he had been secretly paying for escorts.

HOW TO TELL SOMEONE THEIR PARTNER IS CHEATING

Finding out about someone’s partner being unfaithful can put you in a tricky position. Handling it carefully can reduce harm and respect boundaries.

1. Pause Before Reacting

Take a moment to process your emotions before doing anything.
Avoid rushing in with anger or accusations - this can make the situation worse.

2. Assess Your Role

Consider your connection to the people involved. Are you directly affected, or are you an outsider?
Ask yourself if telling them is your responsibility or if it could cause unnecessary harm.

3. Gather the Facts

Be sure of what you know - avoid assumptions or gossip.
The more factual and concrete your information, the easier it is to communicate clearly.

4. Give the Cheater a Chance

If appropriate, consider allowing the partner who cheated to come clean first.
Sometimes a direct confrontation from the cheater themselves can reduce shock and conflict.

5. Weigh the Pros and Cons of Telling

Consider potential outcomes: Will telling them help them make informed decisions about their relationship, or could it cause unnecessary pain? Could it escalate conflict or affect others around you? Are you prepared for the possibility that they may not believe you, or may react with anger or denial?
Think about timing, privacy, and emotional readiness.

6. Approach the Conversation Thoughtfully

Choose a private, calm and neutral setting where the person can process the information without distractions or an audience. Ensure it’s a safe space for an honest conversation.
Stick to facts; avoid judgmental or inflammatory language. Focus on what you know, not opinions or assumptions.
Be brief and compassionate - your role is to inform, not solve or mediate.

7. Respect Their Response

Allow them time and space to absorb the information, and avoid pushing for immediate decisions or reactions.
They may need time to decide how to act, or they may not believe you immediately.
Respect their decisions, even if you would choose differently - they have the right to handle the situation in their own way and on their own timeline.
Avoid pressuring them or trying to influence the outcome.

Ask me and my counsellors anything

Every problem get a personal and private reply from one of my trained counsellors within one working day.

Sally Land is the Dear Deidre Agony Aunt. She achieved a distinction in the Certificate in Humanistic Integrative Counselling, has specialised in relationships and parenting. She has over 20 years of writing and editing women's issues and general features.

Passionate about helping people find a way through their challenges, Sally is also a trustee for the charity Family Lives. Her team helps up to 90 people every week.

Sally took over as The Sun's Agony Aunt when Deidre Sanders retired from the The Dear Deidre column four years ago.

The Dear Deidre Team Of Therapists Also Includes:

Kate Taylor: a sex and dating writer who is also training to be a counsellor. Kate is an advisor for dating website OurTime and is the author of five self-help books.

Jane Allton: a stalwart of the Dear Deidre for over 20 years. Jane is a trained therapist, who specialises in family issues. She has completed the Basic Counselling Skills Level 1, 2, and 3. She also achieved the Counselling and Psychotherapy (CPCAB) Level 2 Certificate in Counselling Studies.

Catherine Thomas: with over two decades worth of experience Catherine has also trained as a therapist, with the same credentials as Jane. She specialises in consumer and relationship issues.

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My sister has met man of her dreams & says they’re ready to start a family… Should I tell her boyfriend’s d...