Serena and Venus Williams set up Australian Open final showdown

Death, taxes and the Williams sisters.

There are few constants in life, but Serena and Venus Williams still continue to reign atop the tennis world, even well into their 30s.

Thursday in Melbourne, Australia the sisters achieved another milestone, each advancing to the Australian Open final. There, they will face each other for the ninth time, and the first since 2009, for a Grand Slam title.

A Serena Williams win would be her 23rd Grand Slam title, surpassing Steffi Graf for most in the Open era.

Up first, elder sister Venus Williams, who turns 37 in June, won a grueling semifinal match against fellow American CoCo Vandeweghe, 6-7 (3), 6-2, 6-3.

Venus Williams and Vandeweghe, both heavy hitters, came out swinging in Melbourne. The opening set began with two breaks of serve. Though largely Venus Williams outplayed her 25-year-old in the opener, Vandeweghe kept fighting, with five aces and seven winners, and pulled it together in the tiebreak to take a one-set lead.

Visibly frustrated by the deficit, Venus Williams buckled down. She stormed out to a 5-1 lead in the second, firing eight aces and winning 82 percent of first serves to take things to a decider.

In the third set, Venus Williams’ experience turned out to be the difference over her younger opponent.

While Venus Williams took her time in defeating her foe, Serena Williams took care of business in orderly fashion, finishing off Mirjana Lucic-Baron, 6-2, 6-1 in just under an hour.

Younger sister Serena, 35, owns the overall Grand Slam final series 6-2. The last time they played in an Australian Open final came in 2003, when Serena captured her first “Serena Slam.”

And, fittingly, the first time the sisters ever met in a Grand Slam was at the Australian Open in 1998.

“She’s basically my world and my life,” Serena Williams said. “To meet in the final … is the biggest dream come true for us.”