By Martyn Herman

LONDON (Reuters) - It was quite a couple of hours for the Murray brothers at the ATP World Tour Finals on Friday.

Younger sibling Andy crushed Switzerland's world number three Stan Wawrinka 6-4 6-2 to top his group and stay on course for a season-ending finale against Novak Djokovic.

Shortly before taking to the O2 Arena court, it was also confirmed that Jamie Murray and Brazilian partner Bruno Soares would end the year as the world's top-ranked duo, courtesy of a defeat for rivals Nicolas Mahut and Pierre-Hugues Herbert.

Jamie has made a habit of beating his higher-profile brother to milestones.

He won a grand slam title -- the 2007 Wimbledon mixed doubles -- five years before Andy won the U.S. Open.

Jamie reached number one in the ATP doubles rankings in April, seven months before Andy hit the singles summit.

Now he has clinched the year-end top spot for the first time with Soares, a few days before Andy can match him and confirm he is the top dog in men's tennis.

Jamie could also beat his brother to the ATP World Tour title as the doubles final on Sunday is the warm-up act for the singles.

"Regardless of what happens over the weekend, we can look back on this year and be very proud of what we've done as a family," said triple grand slam champion Andy.

It looks odds-on that Murray junior will meet Serb Djokovic in the final when not just the title but the year-end number one ranking would be up for grabs.

Djokovic, who faces Kei Nishikori in his semi-final on Saturday, cranked up the pressure on Thursday by trouncing David Goffin in his final group match, edging just ahead of Murray on points.

Murray faced a far trickier task against U.S. Open champion Wawrinka. After weathering an early storm, he won with something to spare to extend his winning streak to 22 matches and set up a semi-final against Canadian Milos Raonic.

A straight-sets defeat could have eliminated Murray and he knew that simply winning a set would earn a semi-final spot.

MANGLED RACKETS

Wawrinka, still harboring hopes of reaching the semis for a fourth year running, began aggressively but a netted volley in the seventh game handed Murray the first break.

The Scot failed to convert three set points at 5-3 but was dominating the match by then and held in the next game.

After spending three hours 20 minutes grinding past Nishikori on Wednesday, Murray was not keen on more overtime and broke twice to romp through the second set -- Wawrinka mangling two rackets as his hopes faded.

"The first set was tight, there weren't many chances," he said. "The second I had already qualified and Stan needed to win so it was a bit easier for me to play freely."

Murray's winning streak equals his run earlier this year. Two more victories would deliver his maiden ATP World Tour Finals title while depriving Djokovic of a sixth, and the season-ending top spot.

First, he must get past Raonic for the third time in a major clash in London this year, having beaten him in the final at both Queen's Club and Wimbledon in the summer.

"I'm certainly not taking anything for granted. I know it will be hard," said Murray whose brilliant late-season run has landed him four consecutive titles.

Round robin play concluded later as already-eliminated Croatian Marin Cilic warmed up for next week's Davis Cup final against Argentina by beating a tiring Nishikori 3-6 6-2 6-3.

It was his first win in six matches at the tournament and the 200 ranking points he earned means he will move above Gael Monfils to a career-high six.

(Editing by Tony Jimenez and Ian Chadband)