TO an outsider, my youngest sons might give the impression they cannot stand the sight of each other. They don’t speak to each other at school.

Unless the sort of defiant grunt which follows after one of them thumps the other on the arm when they pass in the corridor counts.

They shared a bedroom until they were aged eight and 11. And for most of those years, the bulk of my early evenings were spent tearing up and down stairs settling arguments or breaking up fights.

It usually wasn’t even over anything significant. A major conflict could erupt over one of them claiming the other was ‘breathing funny’ or because ‘he keeps looking at me’.

As older brothers freed up rooms when they left for university, we managed to separate the younger two eventually. But the disputes and skirmishes continued.

“You’re the worst brother ever,” one will shout to the other as an item is hurled across the room or a door is banged in fury. I shudder when, albeit rarely, I hear those dreaded words: “I hate you.” Or, even worse: “I wish you were dead.”

“You don’t mean that. You love each other really, you’re brothers,”

I tell them. They look at me as if I am unhinged. But then something happened last week that really put their relationship to the test.

One of them found himself in a situation that is, simply, every teenager’s worst nightmare. He broke his phone.

To most adults, this is a rather irritating inconvenience, but no more than that. We remember life before mobile phones came into existence and can get by with emails and the landline until we get it fixed. But to teenagers, life without access to WhatsApp, texts and Snapchat is the equivalent of being taken off social life support. Being phoneless cuts them adrift from their social sphere, condemning them to a harrowing life of solitary confinement.

They are shut out of all the arrangements being made and conversations being had on their group chats, and they can’t even access their music, which is all downloaded, any more.

Albert looked on in horror as his older brother frantically made a few calls on the landline, in an attempt to sort out the mess. Roscoe’s screen had shattered when he dropped it on a night out and he wasn’t able to access anything on his phone now. The insurance excess meant claiming for a new one wouldn’t be worthwhile, especially since he’s due an upgrade soon.

He found a man in Darlington who could come to the house and fix the phone for £80, but he couldn’t do it for a couple of days. And in a couple of days, Roscoe was heading off on an InterRail trip across Europe with some friends.

Now he faced doing this without a phone. When I mentioned that I went on an InterRail trip at his age without a phone, that didn’t help.

Because, obviously, I grew up in the Dark Ages.

The brothers looked at each other.

They understood. Because, in their minds, there was no doubt. This really was a particularly distressing man-made disaster.

The next day, Roscoe seemed happy as he packed his bags. “Have you managed to sort it?” I asked.

“Yes, Albert gave me his phone,” he said.

I was stunned. For surely, in modern childhood, greater love has no man than this: to lay down his phone for his brother.

I was convinced Roscoe must have bribed him, perhaps pledging half his future earnings for the next ten years, or at least to agree to sole use of the PlayStation.

“You gave him your phone? How come you did that?” I asked Albert.

He shrugged his shoulders: “He asked me,” he said, just like that.

I was, momentarily, stunned: “You see? You do love him really,” I said.

“No I don’t,” barked Albert, horrified.

I was still full of pride a few days later: “I think what you’ve done for your brother is just wonderful. To go without your own mobile phone for three weeks while he’s away really is above and beyond what anyone could expect.”

He looked at me, astonished: “Three weeks? I thought he was only away for a week!”

I expect they’ll have words when he gets back.