Serena, 35, is bidding for an Open-era record 23rd Grand Slam, while Venus, 36, is targeting her eighth major and first since Wimbledon in 2008.
“This probably is the moment of our careers so far,” said Serena, who has beaten Venus in six of their eight Grand Slam finals.
“I never lost hope of us being able to play each other in a final.”
Saturday will be their first Grand Slam final against each other since Wimbledon 2009 when Serena won in straight sets and their 28th meeting in total.
“Nothing can break our family,” added Serena. “If anything, this will definitely bring us closer together, knowing that I want to see her do the best that she can possibly do.
“I know that she definitely wants to see me do the best that I can do. This is a story. This is something that I couldn’t write a better ending for. This is a great opportunity for us to start our new beginning.
“It’s the one time that I really genuinely feel like no matter what happens, I can’t lose, she can’t lose. It’s going to be a great situation.”
Serena drew level with Germany’s Steffi Graff on 22 Grand Slams when she claimed her seventh Wimbledon title last year but lost in the US Open semi-finals to Czech Karolina Pliskova.
A seventh title at Melbourne Park would add further credit to her claim as the greatest of all time, despite being one short of Australia’s Margaret Court, whose 24 major titles were split between the amateur and professional eras.
Venus failed to reach a single Grand Slam quarter-final between 2011 and 2014 as she battled injuries and Sjogren’s syndrome, an auto-immune disease that causes fatigue and joint pain.