By Ian Ransom

MELBOURNE (Reuters) - Having seen her sister Venus win her semi-final at the Australian Open on Thursday, Serena Williams admitted she felt the weight of history to seal her place in their first grand slam title decider in eight years.

That pressure was converted into a rampaging 6-2 6-1 win over Mirjana Lucic-Baroni that ended the 79th-ranked Croatian's fairytale run at Melbourne Park and put Serena into a 29th slam final.

It took only 50 minutes for Serena to book the family reunion after Venus's tough three-set win over unseeded Coco Vandeweghe at the same Rod Laver Arena court.

But a whole tennis era has passed since the Williams sisters last met on a comparable stage at the 2009 Wimbledon final.

Serena won in two sets that day and has since added another 11 grand slam singles titles to extend her tally to 22, a professional-era record she shares with Germany's Steffi Graf.

But for seven-times grand slam champion Venus, Saturday's final will be her first at a major since that grass court encounter.

"It felt really good because I felt like it was in my hands to force this Williams final," Serena told reporters of her semi-final rout.

"Believe it or not, I was feeling a little pressure about that, but it felt really good to get that win.

"I didn't think about it, but I guess it is an old familiar feeling that I clearly forgot about.

The 35-year-old world number two was back to her ruthless best against 34-year-old Lucic-Maroni, their aggregate ages making it the 'oldest' grand slam semi-final clash in the professional era.

But it was the younger opponent moving with more weight in her legs as Williams charged out of the blocks to wrap up the first set in 25 minutes.

The second was of identical duration and of a similar pattern, with Williams in full flight and Lucic-Maroni surrendering quickly with a forehand slapped into the net.

The Williams sisters were near the top of their game when they met in the Wimbledon final and though their paths have diverged, they have both suffered huge setbacks off court.

Serena has overcome a major health scare and a litany of injuries while Venus has made her return after years battling Sjögren's syndrome, a long-term auto-immune disease that causes fatigue and joint pain.

"I think, of course, I was always stressed out and worried if she would be okay and be able to play," Serena said of her older sister's struggles.

"I would see her practise, she'd practise so well, do so well. I always felt like when she lost, I was almost surprised... At the same time I was like, 'Wow, it's amazing that you're even out here'.

"I just really feel fortunate to have been there for the

highs and the lows and everything."

(Editing by Peter Rutherford and John Stonestreet)