Castle is the father of Alexis Castle and the son of Martha Rodgers, both of whom live with him. His father is a CIA operative who has used the aliases "Jackson Hunt" and "Anderson Cross". Castle's birth name is Richard Alexander Rodgers; he uses Richard Edgar Castle as his "nom de plume", (Edgar in honor of Edgar Allan Poe, though he still considers Alexander his middle name). Fillion describes the family dynamic as unconventional because "Castle is very much mothered by his 15-year-old daughter, and at the same time he turns around and mothers his own mother."