My 39-year-old brother-in-law is dependent on his parents. What can we do?

My 39-year-old brother-in-law still lives with his parents, taking pocket money from them and allowing them to pay for everything for him (including business-class flights). He has never not lived with them; even when he was studying abroad at university, he lived in the family apartment that his parents paid for.

He is a nice and easygoing person and has a good job, but doesn’t appear to have any friends and has never had a serious girlfriend. I want to be compassionate towards him, and want him to have a better and fuller life, for his own sake. I have spent over 10 years discussing with him (and, separately, with his mother) how he plans to move out and live his own life, even helping him look at apartments, but it never actually happens. He has few life skills, and can’t seem to do anything for himself when his mother is not there.

My husband and I feel frustrated and sad that my brother-in-law is letting his life pass him by, especially since he is nearly 40 and says he wants to get married and have kids. We also feel frustrated at the co-dependence of him and his mother, and that the money spent on him could be used for his parents’ retirement. What can we do?

Eleanor says: The first thing you can do is recognise whose problem and life this is: his. It can be agonising to watch someone we care about waste their potential, but you’ll only get into a cycle of mutual resentment if you experience that frustration as your own – as though he’s thwarting your expectations and vision of a good life, not his.

The next question is: is this something that he or his parents would like to change? That’s the only fulcrum on which real change ever turns. Motivation and self-respect just aren’t the kinds of things we can sustain for very long when we’re doing them for someone else’s sake. It’s unlikely he’ll make lasting change because others think he should – he’ll have to come to think that, too.

So how (if at all) can you get someone to want to change? The pragmatic reality may be that even though the situation frustrates you, expressing that could make things worse. This is someone who – for reasons that are his own concern, best discovered by a professional – chooses to stay with his parents instead of pursuing the life he says he wants.

Unless there’s some concealed explanation like an illness or a request from them that he stay on, he seems like someone who finds more comfort with Mum and Dad than out in the world. If he senses you regard him as juvenile or failing, the risk is he’ll only have more need for the comfort that keeps him at home.

Perhaps your best bet is to come from the opposite direction. To strike out on his own, your brother-in-law might first need to believe that he’s capable of doing so. This is difficult, because so far he has very little evidence that he is. One of the weird internal structures of big changes is the way they require a kind of irrationality. We have to be able to set aside all the evidence about what kind of person we are, based on choices we’ve made until now, and be guided instead by the hope that we could make a different choice. This is unreal levels of hard, but true – sometimes people need to feel big to make big changes. Perhaps, instead of focusing on the ways he’s making himself small, you could focus on the ways he could feel bigger.

Is there a hobby or an activity he’s genuinely excited about? It doesn’t matter how small it is. You could encourage him to chase it – enter a tournament, teach you more about it, meet other people who do the same. Excitement about anything can restore a bit of agency and energy, ideally in a way where trying doesn’t risk failing. The more muscle memory he can develop for what it feels like to independently pursue something, the better.

And perhaps you could confect some opportunities for him to learn those life skills. Sometimes people only learn something once they experience the consequences of being unable to do it. Could you try to rely on him in small-scale ways – need a hand moving, ask for help fixing a sink, ask what he’d do with a tricky work problem? Things that force him to feel what it’s like to solve something.

If he can’t be moved to even small displays of excitement or problem-solving, I think then it would be time to ask whether he’s privately battling a depression, in which case your role is different all over again. In the meantime, though, try to separate the reactions you’re allowed to have from the reactions that are likely to help.

This letter has been edited for length