Compare Phoebe with both Holden and Allie.  How is she similar to and/or different from her brothers, according to Holden’s description of her?

In Chapter Ten, Holden describes his family in more detail in the course of this chapter. His sister Phoebe is the smartest little kid that he has ever met, and Holden himself is the only dumb one. Phoebe reminds Holden of Allie in physical appearance, but she is very emotional.