Alexandra is the daughter of Sean Astin (Samwise Gamgee) and his wife Christine Astin. She comes from a family of actors that include people like Patty Duke and John Astin. She has two younger sisters, Elizabeth, b. 2002, and Isabella, b. 2005. She has appeared and attended with her father book signings and the promotional tour of There and Back Again: An Actor's Tale.
The part of Elanor is Astin's only known role in cinema so far.
Her nickname is "Ali".