- Judy Murray reveals sons Andy and Jamie used to bicker as youngsters
- Brothers are key members of Great Britain's Davis Cup team
- Both grand slam champions, they will play in Davis Cup final in November
(CNN)They breed fighters in the Murray family -- literally.
It didn't matter what game tennis stars Andy and Jamie played as youngsters, it would usually descend into a spot of sibling fisticuffs.
Both major champions in their own right now, and the crucial axis in the Great Britain (GB) team due to contest the Davis Cup final next month, their squabbles often had their mom tearing her hair out.
"It didn't matter what it was; cards, dominoes, monopoly, golf or football, they were always competing with each other," Judy Murray told CNN's Open Court show.
"They had a lot of fun as well as a lot of fighting. They made up their own games and they made up their own scoring systems and their own rules.
"I can't say they even played or trained a lot of tennis together because they didn't manage to last half an hour without fighting with each other!"
The pair have followed different paths in tennis but each has scaled the heights in their respective disciplines.
Andy is a two-time grand slam winner in singles, delighting Wimbledon with his victory in 2013, adding it to the U.S. Open crown he won the previous year.
Weeks before that first grand slam success, Andy had secured an emotional gold medal victory over Roger Federer in the Olympic men's singles final at Wimbledon.
Jamie was the first Murray to become a Wimbledon champion though, teaming up with Jelena Jankovic to win the mixed doubles title in 2007.
The brothers' partnership has been pivotal in seeing GB through to its first Davis Cup final since 1978, an epic five-set semifinal doubles win over Australia the undisputed highlight.
The brothers in arms have come a long way since the days when those arms were deployed in an altogether less brotherly fashion.
"The story that always springs to mind was when they played against each other at a tennis tournament," Judy explained.
"I had taken a lot of children down from Scotland. I'm driving back in the mini-bus, it's quite dark and Andy has beaten Jamie in the final of this Under-12 event.
"They start having a fight in the back of the mini bus. Andy's hand is over the back seat and eventually Jamie has taken enough and nails his fist into Andy's hand.
"There was blood and I had to stop the bus, we dress the wound, separate them and drive the few hours back.
"We had to take Andy for a tetanus shot because the nail was ripped and the nail has never grown in straight. But it's a reminder about being humble and never bragging about beating anyone -- especially your brother!"
Both brothers were gifted in many sporting spheres as youngsters -- Andy having to decide between tennis and soccer aged 14, and Jamie excelling at golf.
Judy thinks Andy's "mega-competitive spirit" was fueled by his brother being "bigger and better" at most things while they were growing up.
In that case, despite the bickering, Andy probably owes Jamie a debt of gratitude for imbibing a tenacious spirit that currently sees him sitting at number two in the world rankings.
"Jamie is without question Andy's number one fan," said Judy, dispelling the myth that any jealously exists between the two. "He's always absolutely delighted for his brother.
"They are the only people I think of who can really say what they are thinking straight to each other's face. There are not that many people who can do this, particularly with Andy nowadays."
A punishing schedule on the Tour means both Murrays often head into a Davis Cup tie on the back of a grueling grand slam campaign.
But in both the quarter and semifinals, Andy has played in three of the five rubbers, teaming up with Jamie for the doubles leg either side of his two singles matches.
Fatigue has definitely been a factor to negotiate, not helped by the added pressure of knowing that GB's progress effectively rests on his shoulders.
"If he doesn't win his matches, we don't win the tie. It's as simple as that," reflected Judy.
It was Andy that took GB through to a first Davis Cup final for 37 years with victory over Australia's Bernard Tomic in Glasgow in September. Led by Fred Perry, GB last won the Davis Cup in 1936.
"You can see that when you are really that determined -- he just gets that 'Braveheart' thing going -- you find an inner strength from somewhere, even if you are hurting or exhausted," adds Judy.
"The fact that we have had so many home ties I think has really helped him and the crowds have been very special -- they've helped him to find something when he might not have been feeling his best.
"It's a different emotion playing for yourself over playing for your country. Very rarely you'll see him going nuts when he wins an individual title but in the Davis Cup I think he feeds off the crowd."
Judy has a long history in tennis herself.
A coach of the game for over 20 years, she has a close association with the current Davis Cup captain, Leon Smith, who worked for her in the Scotland set up.
She also knows a thing or two about team competition, having coached GB's women in the Davis Cup equivalent -- the Fed Cup -- since 2011.
So how does it feel having gone from hitting sponge balls around a school hall with her two sons in a small Scottish town to roaring them on as they strive for a significant piece of history for their country?
"When I watch them playing doubles, that's the most emotional time," she said. "It's quite amazing to see your kids playing together for their country.
"Against France, up to that point Andy hadn't played a lot of doubles over the past few years because he was protecting his back.
"Jamie, of course, is a doubles specialist, so he took the lead and did it incredibly well.
"Some of the things Andy said afterward about sticking together when times are tough like brothers should, bring a lump to your throat."
GB face Belgium in the Davis Cup final that starts on November 27 and, of course, the Murrays will be there mob handed.
"The whole family is going," Judy said. "This is a very special moment for the family with both boys playing and it's potentially a moment in history -- it's a big, big moment in their lives.
"We'll sit with the British part of the crowd and make as much noise as we can."