You know you’re the luckiest person alive to have landed your perfect partner, but when it comes to their relations, the laws of probability may not be on your side. You’ve upset the balance of their family: at best you’ve swelled the ranks, further dividing the pot of love and attention; at worst you’re the cuckoo in the family nest, stealing their beloved son/daughter/brother/sister.

Even wonderful in-laws can create problems. If they’re warm, uncritical, unfailingly supportive, always pleased to see you, dedicated and hands-on with their grandchildren and generous at Christmas-time, this might play merry hell with your relationship with your own less-than-perfect parents or siblings. Families can be fiercely competitive, and you may find yourself the focus of an undignified tug of love, which can be extremely painful if children are involved.

Treat a bad in-law as you would childhood chicken pox. You don’t want it, you don’t deserve it, you can’t really do much to alleviate it but it’s a necessary evil and if you stay calm and are careful not to aggravate it, you’ll come out barely scarred. Comfort yourself with the thought that your partner chose to leave the bosom of his/her family and create a new family with you – if the in-laws are truly toxic then your cleverest plan is to sit tight, behave immaculately and trust that there will be no doubt about which family is the better bet. As for perfect in-laws, don’t boast about them to your own family (that way lies perdition), just secretly rejoice in your good luck.

Golden Rules for In-Laws

• It’s your job to interpret your own family dynamic, customs and traditions for your partner. Don’t just leave your partner to sink or swim, give them some warning about no-go areas, things your family cherish, well-established family rituals, family feuds. This should be reciprocal, so you will be well briefed when it comes to dealing with your in-laws.

• Behave impeccably at all times. Whatever the provocation, keep your mask of good manners intact.

• If you are subjected to criticism of your housekeeping, child-rearing etc., smile graciously. Try and ignore the criticism, treating it as merely irritating white noise.

• If the criticism persists, you could opt for humour and self-deprecation. Shrug, smile charmingly, say ‘you’re probably right… I was always hopeless at this kind of thing’ and move on. With any luck your charm and good grace will show them up for the carping, sour-faced critics they really are.

Alternatively, you can go for the out-and-out adulation defence. Just turn your face into a mask of awe-struck admiration, sit (figuratively) at their knees and ask them to teach you everything they know. Alternate intent listening with nauseatingly effusive compliments, and they’ll soon get fed up with the mentoring role.

• Whenever possible, ask for advice from your in-laws (for example on financial or house-related matters, or parenting). They will feel flattered to be asked – after all, everyone likes giving advice. You will have your own views about whether to follow it.

• Try not to criticise your husband or wife to your in-laws. Even if they’re sympathetic and think their son/daughter is a bit of a wastrel, you can be sure that, at some level, visceral loyalty will eventually kick in. Your confidences may come back to haunt you and, if that is the case, will certainly be held against you.

• Similarly, be very careful about criticising your in-laws to your husband/wife. This isn’t necessarily a no-go area – some couples find criticising their parents’ behaviour both therapeutic and helpful – but you need to be sure that criticism isn’t going to elicit a defensive reaction, or be held against you in the future.

• Always stick up for your partner. You may find in some families that your support is enlisted when it comes to berating an errant son or daughter. No matter how tempting it is to side with your in-laws and reap the benefits, remind yourself that your first loyalty is always to your partner. If his or her parents’ criticisms are legitimate, they should be discussed later and in private.

• Take the lead from your partner when it comes to relating to your in-laws. You may enjoy chatting to your mother every day, while your husband rings his once every six weeks. Don’t berate him for the lack of contact; accept that every family dynamic is different.

• Whatever you do, ensure that both you and your partner present a united front. This is particularly important when dealing with potentially difficult issues, for example plans for Christmas.

• If you have reached a point where the in-laws really must be confronted – perhaps you have found their babysitting worryingly deficient or their interference in your life has become unbearably onerous – this must be done together. It is always a bad idea for you to take the lead role in any confrontation; your partner’s loyal support is imperative.

• Remember that good manners will get you a long way when it comes to building a relationship with your in-laws. Send thank you notes for hospitality and presents, and ensure that your children are similarly effusive. Bring gifts of flowers or drinks when you’re visiting. Note down birthdays and anniversaries and send cards and presents. Always remember to thank you in-laws for any help they have given you, for example babysitting or DIY, and never take these kind gestures for granted. Even if your meticulous courtesy is not appreciated, you will know you have done the right thing and cannot be found wanting.

• If all else fails, and you find yourself in an increasingly pernicious relationship with your in-laws, you should speak diplomatically to your partner and explain why you are finding it difficult. You may be able to negotiate with your partner about the amount of time you spend together – he or she might be willing to visit their parents on their own from time to time. It will help family harmony if you can manage to find a compromise; conceding that you owe it to your partner to spend some (limited) time with his or her parents, no matter how difficult, will certainly be less damaging than estrangement.

• Above all, remember your in-laws are individuals in their own right, not simply your partner’s parents. Their personalities and way of life have been formed by their own history, experiences, and family background. Don’t let your partner’s over-familiarity inform your own relationship with his/her parents. Make an effort to really get to know them – listen to their stories, look at family photographs, exchange confidences. The chances are that, by taking an interest in them as human beings, you will find new ways of making a success of this vital relationship.