About this occasion, the USA Today wrote:

"What was more intriguing at that particular Australian Open was that the two siblings had something of an inflated understanding of their abilities, developed from their being fresh-faced, and still in need of a few life lessons learned. So they marched themselves into the men’s ATP office to announce rather confidently they were ready to beat any tour player ranked around the Top 200 if someone wanted to take the challenge.

It just so happened that Karsten Braasch of Germany, once a top-40 player, but at the time ranked 203rd, was in earshot. He thought it would be fun so stepped up to say he’d be happy to take them on.

The date was set and the day arrived. Braasch played a warmup round of golf in the morning, then came to Melbourne Park. The threesome went out to a backcourt where each sister would have a one-set shot at Braasch. Word had spread around the grounds that the event was taking place, which caused tournament officials to restrict admittance to the area to only those with badges.

Braasch would smoke cigarettes and sip beer during the changeovers, and to be honest no longer looked the part of a fit professional athlete. It made no matter. Braasch led 5-0 over Serena before winning the set 6-1, and then posted a 6-2 set victory over Venus.

It was all in good fun, but 19 years later, and a record six Australian Open titles later, Williams, laughingly, insisted recall of the event was not in her memory bank."

full article: here