Jonathan Davies refuses to share a room with his brother James - who he says is too messy - but he will make an exception on Saturday.

That's because they will both be in the home dressing room at Cardiff's Principality Stadium, ready to become the first brothers to play for Wales since Jamie and Nicky Robinson in 2006.

This World Cup warm-up match against England will not be the first time the Davies brothers have been team-mates - they are long-time regional colleagues at the Scarlets - but representing their country together will certainly be a novelty.

Centre Jonathan, 31, will be winning his 75th Wales cap, while this will only be a fourth appearance for 28-year-old flanker James.

Seniority rules for the elder brother, then, both in terms of age and status in the squad. Was it always this way?

"I've got a better record in the garden than him," Jonathan grins.

"He's alright, he can handle himself. It's great news for him and I'm looking forward to seeing how he goes.

"He's worked hard over the summer. He's always given a good account of himself and I'm sure he'll do that on Saturday."

It was those childhood duels in the back garden which helped give the Davies brothers their nicknames.

Because their parents ran the Fox and Hounds pub in Bancyfelin, Carmarthenshire, Jonathan earned the moniker 'Fox', which is why his younger brother is known as 'Cubby'.

Those have stuck and, in James' case, to such an extent that he has tattooed the words 'Cubby Boi' with a letter on each finger.

He is the practical joker of the two, a loud character who is as renowned for his eccentric social media persona as he is for forcing turnovers and scoring tries.

"I can't share a room with him," the calmer, more placid Jonathan says about his boisterous younger brother.

"He lived in my flat a few years ago and it was awful! He's very messy."

The brothers were both playing for the Scarlets when they lived together in a flat in Cardiff but, since Jonathan's return from a two-year stint with Clermont Auvergne in France in 2016, the two live apart.

Most brothers will attest that a little distance or time away from one another is healthy; a break from the teasing, the berating and the intense competitiveness, whatever the game.

Despite the drawbacks, sibling rivalry does have its advantages, such as a fierce will to win shaped by countless brotherly clashes.

The Davies' rugby careers are a case in point but, when they were growing up together, neither gave much thought to the idea that they would be Wales team-mates one day.

"No, if I'm honest," says Jonathan.

"It's something I'm sure when we look back on we'll be very proud.

"Mum and dad and my sister will be very proud as well. We're preparing to hopefully go to a World Cup and we're not going to sugar-coat it at all this weekend.

"We want to go out there and give a great account of ourselves and warrant a seat on the plane to Japan."

Japan-bound?

As one of the world's best outside centres and a veteran of two British and Irish Lions tours, Jonathan is guaranteed to be in Wales' final 31-man squad for the World Cup.

That is fitness permitting, of course, as he missed international rugby's showpiece event four years ago because of injury.

The equation is not so simple for James, who has suffered with a raft of injuries himself in recent seasons.

Even if he proves he is over his back issues and other ailments, the open-side flanker will be vying for a place in what is arguably the most competitive area of the Wales squad.

Taulupe Faletau has been ruled out after breaking his cavicle but Wales' back-row options still include Justin Tipuric, Josh Navidi, Ross Moriarty, Aaron Wainwright and Aaron Shingler.

It could be that head coach Warren Gatland only selects five back-rowers to take to Japan, so a rare Wales start against England on Saturday could have a huge bearing on James' hopes of being included in the final squad.

"It's a fantastic opportunity for him," says Gatland.

"We were really impressed with him in Argentina [during the summer 2018 tour] and he's pretty fired up.

"He's someone who's said all his career that everyone's knocked him, said that he's too small, not able to compete at the highest level and we've probably had some of those thoughts as well.

"But having coached him and been involved with him in Argentina, we were incredibly impressed with him.

"It's a great opportunity for him and the first time in a long time that two brothers have played for Wales as well."

When fit, James has impressed in his limited appearances for Wales; disruptive at rucks and an attacking threat when he has the ball in his hands in wide areas.

And after overcoming his latest injury setback, he will not have to look far for inspiration on Saturday.

"Using the drive and hunger to want to get back to the top level helps everyone get over these injuries," his big brother Jonathan says.

"He's worked hard over the summer and he's got the chance he deserves."