London Irish's clash with Bath on Saturday brings rugby's first belated battle of the Joseph brothers with 20 members of their family expected at Brentford... and Will has a point to prove against big brother Jonathan

• Jonathan and Will Joseph will go head-to-head for the first time this weekend
• London Irish take on Bath at the Brentford Community Stadium on Saturday
• Older brother Jonathan, 31, plays for Bath while Will, 20, stars for London Irish
• Both Joseph siblings are suitably fired up for the launch of their on-field rivalry

If the train strikes don't scupper their plans, there should be 20 members of the Joseph family at Brentford Community Stadium on Saturday, for the belated first encounter between Jonathan and Will.

They've all waited a long time for this momentous occasion, so there is a profound sense of anticipation, not least for the brothers themselves. Anticipation and motivation. 

While the siblings have a mutual respect, they are both suitably fired-up for the launch of their on-field rivalry, at last, as Will's London Irish take on Jonathan's Bath.

When the pair meet Sportsmail at their parents' house in Berkshire to discuss the game, their careers and each other, there is nothing which could be construed as trash-talk, but there is bullish intent on both sides.

'We've been waiting for it for a while,' said Jonathan, the older brother – aged 31 and a veteran centre with a half-century of England caps to his name. 

'Two years ago, he was on the bench and didn't get on. Shame on him! Then we were supposed to start against each other but he got injured. He bottled out of that! So it's finally on.'

'I just thought I'd wait until you were a couple of years older,' said Will – who has just turned 20 and made his Test debut in July, after a handful of appearances for Irish. 

'I'm coming in now, ready for the challenge. We'll both be in the wide channels, so I'm sure we'll see each other and have a bit of banter – a bit of brotherly love! I'll make sure I seek you out a couple of times, just to see if you're up for it.'

'Good luck with that,' said Jonathan. 'Because of the age gap, there's been nothing before. We've always said it would be nice to play each other. We've got the opportunity this weekend. We played a bit of tennis when we were younger but I would always batter him!'

'It's all going to change this weekend,' said Will. 'We'll see,' came the retort from across the sofa.

For Will, Saturday's game is a chance to make a statement about his own credentials, having grown up with constant comparisons to the brother whose path he followed, through Millfield School and on into the Exiles' academy. 

Similarities have been highlighted every step of the way, even when he joined up with the England squad and shared a room with Jonny May, who said: 'He looks like JJ, he walks like JJ and he runs like JJ.'

'Yeah, I've had that a lot,' said Will. 'The first time I went into camp, I was on one of the physio beds and Jonny actually said, "Wow, you are literally sat the exact same way JJ would be sat and talking the exact same way". We've got some pretty similar mannerisms. I've had that pretty much my whole life really. At school, the coaches would say similar stuff.

'I'd still say I'm myself and that's why I'm excited for this weekend. I've always been known as JJ's little brother and that was tough for me when I was younger. Having this opportunity… there will still be the comparison but hopefully I can be a bit less in his shadow and be known just as Will Joseph.'

Jonathan added: 'I do see a lot of myself in him.' He spoke of the familiar combination of X-factor and the composure to make good decisions under pressure, while avoiding mistakes – essential ingredients for elevation to international level. But are they similar characters too? 'Yes and no. I'm the first-born so I'm a bit…'

'A bit more arrogant,' quipped Will. 'A bit more privileged!'

'Yeah, yeah,' said Jonathan. 'And he's the last of four. Alex, our other brother, his twin, has special needs, so when he was a kid, Will would always come after Alex. So Will is the perfect boy.

'He would go to tennis club and there would be a situation with Alex, so mum would be an hour-and-a-half late to pick him up and he'd just be sat there like, "It is what it is". Not much gets under his skin, whereas I would be screaming – a proper diva!'

In fact, Jonathan soon dislodged his 'perfect' brother's halo, by embarrassing him with a story. It was in response to a question about how close they are and Will's explanation that the period of Covid-related disruption in 2020 had actually allowed them to spend more time together.

'I'd say over the last three years we've definitely become a lot closer,' said Will. 

'Spending time with J in lockdown was good, because we hadn't seen each other a lot when I was growing up.'

Jonathan chipped in to ask: 'But how did that circumstance come about?' Will awkwardly responded: 'Well, school just finished and he came to pick me up…' But Jonathan didn't let him off the hook that easily, adding: 'Did it?

'I got a phone call from Will asking me to pick him up. It was the day before he was supposed to break up. So I drove down to Millfield and he got in the car. He said, "I've been suspended".

'Basically, they knew school was closing and it was the last time probably all of them were going to be together, all his school mates, so a few of them went down to the pub for a few drinks. They got suspended for it, but that gave us an opportunity.

'It worked brilliantly because I took him home – to my place – and said, "You might as well stay for a few days". Then lockdown happened, so he ended up staying for three months. It was so nice. It was probably the first time we properly got to bond together.

'I'd gone to boarding school when he was still pretty young, then I started my career, then he went to boarding school, so our paths hardly ever crossed. He'd come to the odd game of mine and I'd go to the odd game of his, but we'd only have a few hours at a time together.'

With sister Hannah forging a netball career which has seen her represent England too, the Josephs have established a single-generation sporting dynasty. 'Our household was crazy,' said Jonathan. 'It was so hectic. Fair play to mum and dad, they would drive us all over the place.' 

Fair play to them, too, for providing the right genes? 'Yeah, it seems to be the magic potion,' he added.

Will grew up wanting to emulate his brother, as he watched his professional progress. 'When I was younger, I really idolised him and the teams he played in,' he said. 'So when he was at Irish, I really liked Mapusua and guys like that. When he was with Bath, it was Eastmond and Ford.

'But I did really idolise J, I loved the way he played and I always thought that's what I wanted to do. When he was at Irish, I remember going to pretty much every game and really looking forward to it. One I remember quite well was against Sale. He scored two tries in the last 15 minutes – one was an intercept try and that was pretty special.

'In the Six Nations against Wales when he scored a try – I think that was my first time watching him play for England and that was a really special moment for me and the whole family. I remember him scoring and there was so much excitement and joy. We were just so happy for him.'

The sibling pride equation was reversed a few months ago when Jonathan made sure he was able to watch Will's England debut – as a replacement against the Wallabies in Brisbane – from afar. He couldn't be there in person, due to an important social event in Spain.

Will said: 'J was on his stag do and I remember telling him that I would be involved at the weekend, so he just said, "For goodness sake, I'm going to have to rearrange my plans and get up early to watch you"! I called him after the game and he was with all his mates, having fun.'

'I was in Marbella,' said Jonathan. 'I was in a bar watching his debut. It was such a nice feeling seeing him coming on. It was a weird emotion for me. I'm not really an emotional guy, but it definitely felt good seeing my brother out there.

'He's exceeded expectations. I always knew he was going to be good, but I didn't think he would get to this point, this quickly. He couldn't train for a whole year; his injury was that bad. He wasn't even allowed to go to the gym. I know how hard that was for him. He was really down at that point.

'I remember watching his first couple of games back and being so impressed with his ability to not make many mistakes, but still show unbelievable X-factor and do the right things at the right time. That has got better and better as time has gone on. Being on the England tour will have helped him massively; playing alongside great players, learning off them and learning off Eddie (Jones).'

Jonathan and his Bath team-mates will be on a state of high alert on Saturday, about the threat posed by Will and the Exiles' other newcomer in the Red Rose ranks, Henry Arundell. The visitors' No 13 will try to get the better of his brother, but what about the chance of playing alongside each other one day – could that happen?

'Maybe Baabaas,' said Will. 'Yeah, maybe for the Barbarians,' said Jonathan. 'I don't know. We'll see. It would have to be with England or one of us moving clubs.'

For now, they are preparing to be respectful but committed rivals. And 20 relatives will be sat in the stands, with torn allegiances as they savour a profound family event.