Although the 25-month gap in age between our two boys Isaac and Toby is shrinking proportionately as they get older, the differences between them are growing ever wider, in terms of their physiques, personalities and preferences. In fact, the two siblings – fast approaching their fifth and third birthdays respectively – are now as dissimilar in as many ways as they are similar.

We’ve been away for half-term this week, which has given me the opportunity to observe the boys at length without the distractions of work, school/pre-school and busy weekends. For sure, they still have a lot in common: for starters, a shared love of the Cars films, Alice in Wonderland and (regrettably) Gangnam Style. (Although Toby inexplicably remains convinced the song is called Camden Style.)

Physique

But increasingly the differences are becoming more pronounced, starting with their physical appearance. While there’s no mistaking they are brothers Isaac, who originally started out with the same bowling ball-type body that Toby and I share, has recently stretched out into a tall, lean, almost gangly shape. (We reckon he’s the second or third-tallest in his school year of nearly 60.)

Maybe Toby will eventually follow suit, maybe he won’t. But the difference between them at the moment is quite striking.

Personality

When it comes to personality there is significant divergence too. Some of this no doubt arises from the natural differences between a first and second (in Toby’s case also middle) child.

Isaac slots into the role of the responsible big brother, which fits with his naturally cautious outlook. Toby, on the other hand, has always had a daredevil streak in him, happily throwing himself into physical activities which give older children pause. It’s pretty much guaranteed that at some point in the future it will be Toby who falls out of a tree and breaks his arm while Zac busily cordons off the area to prevent future accidents from happening. While wearing a hard hat and a hi-vis jacket. There will probably be traffic cones involved too.

In addition, Isaac is extrovert in his social interactions, craving conversation – he never stops talking – and company, whereas Toby is an introvert who often seems happiest flying solo, doing his own thing quietly. For instance, yesterday we gave him a jigsaw puzzle to occupy him while we packed up to go out, and he didn’t utter a word until he shouted, “Finished!” three minutes later. If that had been Isaac, he would have insisted on one of us sitting with him to talk through it – or, at the very least, we would have been given a non-stop running commentary which would have given John Motson a run for his money. Left on their own, Toby is comfortable whereas Zac looks forlorn.

Preferences

So we have differences in physique and personality, but there are also variations which are more about the boys’ individual preferences.

Some of these have been accentuated by the fact that Isaac is now at school and being exposed to a whole new range of learning opportunities. A couple of instances this week have both amused and bemused me. When working on our Halloween pumpkins, at one stage we fashioned a square nose. Zac’s immediate observation was to note that the carved-out piece was cuboid in shape, and he then explained with great precision how it is different to a cube. Yes, I laughed – but I was also beaming with pride.

Then yesterday we were having lunch at a restaurant, and as we were leaving he glanced over at a print on the wall and casually uttered, “That looks like a Kandinsky to me.” My jaw hit the floor. Not just because he had remembered the artist’s name – it’s not exactly ‘Smith’, is it? – from something they had done recently at school. But, when I looked over, it did appear to be a facsimile of Wassily Kandinsky’s Farbstudie Quadrate. A career on Antiques Roadshow or as an appraiser at Sotheby’s beckons, perhaps?

The fact is Zac has always been studious, conscientious and, well, a bit of a nerd – something Toby shows no inclination of becoming. He has an astonishing memory for facts, events and sounds – from an early age he has been able to name familiar songs from just three or four notes – and generally approaches most things in a cerebral manner. He values precision, he wants to know how things work and he has a logical answer for everything. He learned how to operate my iPhone at the same time he learned to walk, he has taken it upon himself to learn all the road signs from the Highway Code and this week’s latest interest has been learning how to play Ticket To Ride – a Risk-style empire building strategy game –  on the iPad. Let me reiterate: he isn’t five yet.

Whereas Zac is an engineer by nature, Toby has a more creative approach, and this is perhaps most obvious in their art work. You can always trace the logical or observational path in anything his older brother does – a lot of Zac’s drawings verge on the geometric – but Toby is more free-form, more abstract and less concerned about precision. Some of this is just the difference between the skill and motor control of a four and a two-year old, but to my eye there’s also a clear difference in their approach: the analytical logic of Isaac versus the more free-flowing expression of Toby.

More than that, Toby is definitely more of a hands-on practical type, as opposed to his brother who is more of a theoretician (which he gets from me). So, given the opportunity to feed the farm animals this week, Toby has been straight in there with gusto, whereas Zac prefers to observe in the background. Literally, he doesn’t like to get his hands dirty – but he could probably tell you everything you could possibly want to know about the nutritional value of the animals’ diet.

I could go on and on, but you get the idea. Of course, the boys’ differing personalities and preferences are neither a good thing nor a bad thing – they’re just part and parcel of what makes them individuals.  But I find it fascinating to watch them as they develop, grow and change, and to understand how much of who they are is shaped by nature, and how much by nurture – whether it is parental, educational or other environmental influences.

As individuals, we are all essentially the sum of our experiences, and as a father my only real hope for all my children is that the ones that shape them are mostly positive ones. I’m delighted with how they’ve progressed so far.