Since I'm a Texan, I have a natural inclination to love it, and I very much do. However, it's not necessarily a place name, as
Austin is a contracted form of
Augustine, as well as a surname. If you're going with
Augustine, brothers could be
Francis,
Benedict and even
Constantine, while sisters could be
Mary,
Elizabeth and
Catherine.
From your list, I would pair
Austin with
Annabelle,
Audrey,
Rose (remember the Yellow
Rose of Texas),
Savannah and
Scarlett, as well as
Chloe or
Zoe, since
Austin is such a hip, sideways, unexpected sort of place.
Strictly for myself, sibs for
Austin would include brothers Houston,
Dallas, and
Travis (
Austin is in
Travis County), and sisters
Abilene and Daisetta (nn's
Abby and
Daisy). If these ideas come on too strong, there is the perhaps more conservative, less obvious route of, for example, brothers named for
Stephen Fuller
Austin (officially called the Father of Texas)
Samuel Houston (variously President, Governor and Senator of Texas)
David Gouverneur Burnet (President of Texas)
Mirabeau Buonaparte Lamar (President of Texas)
William Barret Travis (hero of the Alamo)
David "
Davy" Crockett (hero of the Alamo)
James "
Jim" Bowie (hero of the Alamo)
Or there could be sisters named
Victoria,
Alice,
Katy,
Melissa,
Donna, and even
Socorro and
Paris - all of which are also Texas towns. If you're more into trendy names, there are
Brady,
Bryan,
Cameron,
Kyle,
Taylor and
Tyler to choose from - also Texas towns.
But that's just the opinion of one Texan woman. =D
Just because I'm on a roll and I feel like adding this info free of charge, here are links to the complete list of names of Alamo defenders, and all the cities and towns in Texas. The namesake of the city of
Dallas, btw, is a matter of some dispute, so I cannot cite an individual to whom credit could go.
http://www.thealamo.org/defend.html
http://www.state.tx.us/category.jsp?language=eng&categoryId=6.1.1