The dilemma I have a 23-year-old daughter. Her mother and I split up when she was seven due to her mother’s infidelity. I still see my daughter regularly and she is close to my wife and the two other children we have. My daughter didn’t have a “proper” boyfriend until she was in her late teens. Last week I was informed that her new boyfriend is a little older than her. It transpires he’s 48! He also has a wife and two children who he is preparing to leave to be with my daughter. I am, in equal measures, furious, horrified, embarrassed, ashamed and desperate. This new boyfriend is older than my wife, who is 46. I am 55. My daughter wants me to meet this man, but I am too shocked and angry that a man of his age and with his responsibilities could behave in this manner. How should I handle this? I am too embarrassed to talk to my friends about it.

Mariella replies I feel your pain. Though I don’t think you have anything to be embarrassed about. Your job was to raise her and teach her how to be the best adult possible. At 23 she may well be romantically naive but she’s a grown-up. Your situation is a parental nightmare, but not the most unusual of scenarios. She’s certainly not the first young woman to fall for an unhappily married mature man.

At the moment I’d say your biggest mistake is to take your daughter’s actions personally. Words like “embarrassed, ashamed and horrified” suggest your immediate concern is not with her happiness but with how her choice reflects on you. Hard as it may be, you need to remove yourself from the equation and try to work out what’s drawing your daughter to what, at very best, will be a complicated partnership. In many ways his age is of less concern than the family he is about to forsake. Having been through a family breakup yourself you are well equipped to understand the legacy of such a separation.

Refusing to engage with him will propel her further into his orbit and dissipate any influence you might have

I’m concerned that your response may be rooted in your ex-wife’s betrayal rather than your daughter’s welfare. Is your anger being exacerbated by still-painful memories of the demise of your own relationship? It’s a plausible explanation for why nearly two decades later you still feel the urge to name and shame your wife’s infidelity as the catalyst for the divorce. Unresolved pain and anger might be pushing you towards your entrenched opposition. I do sympathise with the emotions you describe, but only “desperate” is useful at the moment. It might give you the impetus to overcome your instincts and swallow your pride.

Refusing to meet the man she thinks she loves is a mistake. It puts all the power in his corner by casting you as the intolerant villain. Your first – albeit unappealing – step has to be to meet the object of her affections and treat him with civility. Love can be blind so it’s up to you to take a long, hard look at the man she’s fallen for. Refusing to engage with him will only propel her further into his orbit and dissipate any leavening influence you might have. There’s nothing more compelling in youth than a choice your parents disapprove of. Most epic romances begin with intractable families forcing lovers into each other’s arms. Let’s start with Romeo and Juliet and carry on from there.

I understand why you are vehemently against this union, but if you’re to be the voice of reason you’ll need to work on being more reasonable. Meeting him is a must otherwise your objections are based only on your misgivings, not the individuals involved. An age gap can boil down to semantics once you start arguing about whether a 10-year divide is better than 20 and so on. There are many successful relationships between partners of wildly disparate ages. It may create challenges, but who’s to say they are any greater than cultural or religious divides which are regularly surmounted?

You need to work out exactly what your objections are before you can expect to be given a fair hearing. Few dads welcome the moment their daughters transfer their affections to other men and you do seem to be taking it particularly to heart. Her choice of partner is not your fault, but I know from personal experience that losing your father’s full-time presence at a formative age can leave a vacancy that in adulthood you rush to fill. It could explain her eagerness to establish a family anew.

Your goal should be to create an environment where a calm and reasoned discussion about the responsibilities she is about to find herself shouldering can be had. With that as your focus, familiarise yourself with your protagonist, make tolerance your watchword and try to support your daughter as she negotiates this volatile emotional terrain. Most importantly, separate what’s happening now from your own relationship history. The past is a foreign country so don’t linger on old wounds when the future can still be shaped differently.

If you have a dilemma, send a brief email to mariella.frostrup@observer.co.uk. Follow her on Twitter @mariellaf1