Zac sailed into Marina del Rey last month, after a globe-circling voyage at age 17.
Zac's sister wants to set a record, by making the trip non-stop. However, she has competition for the bragging rights. An Australian schoolgirl, 16-year-old Jessica Watson, is scheduled to set sail in September in an attempt to become the youngest person to sail solo, non-stop and unassisted around the world.
Sunderland's family is behind her record-setting effort. Her parents estimate they'll need $350,000 to cover the cost of the dangerous adventure. They say they're already negotiating with sponsors to help pay for it.
While her brother sailed west out of the Marina, Abigail plans to head for Cape Horn at the bottom of South America. Her father estimates the trip will take six months and cover 24,500 miles.
The Associated Press contributed to this report.