I was once told about a survey which looked at senior executives to determine what factors are most likely to create business leaders. Surprisingly, the one thing which most characterised them was not academics or parental demographics, nor was it gender or race. Instead the research found a marked tendency to have been the first child in the family. When I look at the way Isaac behaves and the way we treat him, I can see what they mean.

Don’t get me wrong, I’m not saying that all oldest children will automatically become leaders. Nor am I saying that Isaac is destined to become the next Richard Branson or Mark Zuckerberg. It’s more that the combination of his position in the family and our parental expectations are more likely to instill in him a set of conditioned behaviours which may better prepare him for some kind of leadership role in later life.

After all, what does a leader do? They are accustomed to stepping up and taking responsibility for things, which is essentially the job description of an older sibling.

There’s no question that we have higher expectations of Isaac than we do of Toby, and probably always will do. It’s not that we think he’s smarter or more likely to become the next David Beckham than his brother, but as the oldest of three children he shoulders the responsibility – and sometimes it’s a burden – of being expected to be ‘the grown-up one’. In practical terms it means that when we’re out and about as a family we expect him to be well-behaved, to be given a greater degree of independence and trust that he won’t do anything silly, and when required to help us out with his siblings. To be a role model and a leader, in other words.

At weekends I often take the boys out for the morning to help me with important tasks like going to the tip and filling up Costa Coffee’s coffers – I really should buy shares – to give Heather a little breathing space. Isaac’s job at such times – one that he relishes – is to help look after Toby, keeping an eye on him, holding his hand as we walk across the car park and generally being the responsible big brother. I think he just likes being bossy and showing off his knowledge as he points out all the different fish on the fish counter in Tesco to Toby, but he plays the role well. He’s much the same in taking Kara under his wing too. He’s a great big brother to have.

All this is a good thing for him in terms of accelerating his maturity and creating a natural sense of responsibility which I’m sure will stand him in good stead in later life, but I do sometimes wonder if we are asking too much of our first child to effectively act as a pseudo third parent on occasion. He is by nature a fairly serious and conscientious individual – much like both his parents – and there are certainly times when we should be encouraging him to just be a boy more. (It says everything about him that his favourite new thing at Christmas was not one of the age-appropriate games we bought specifically for him, but the new version of Trivial Pursuit Heather got for me.)

There is the occasional warning sign to remind us not to push him too hard. Every now and then you can see him struggling under the burden of having to act so grown-up so much of the time. There has been the odd plaintive wail of “I just want to go back to being a baby!” Then ten minutes later he’s back bossing his brother, his sister and, yes, his parents around. But it’s certainly a caution to be heeded.

I want my boy to grow up with a sense of fun. And I want him to grow up ready and willing to be a fully contributing member of society. And I also want him to be an extra pair of hands when I can’t cope on my own. I need him to be all these things, just in the right balance. It’s tough being a father, but it’s also tough being the oldest child sometimes.